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ENTOMOLOGY 














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Some early medical entomology. Athanasius Kircher’s illustration of the Italian tarantula 
and the music prescribed as an antidote for the poison of its bite. (1643). 






























u HANDBOOK OF MEDICAL 
ENTOMOLOGY 


WM. A. RILEY, Ph.D. 

Professor of Insect Morphology and Parasitology, Cornell University 
and 

O. A. JOHANNSEN, Ph.D. 

Professor of Biology, Cornell University 



ITHACA, NEW YORK 
THE COMSTOCK PUBLISHING COMPANY 




COPYRIGHT, 1915 

BY THE COMSTOCK PUBLISHING COMPANY, 
ITHACA, N. Y. 


Press of W. F. Humphrey 
Geneva, N. Y. 


PREFACE 


T HE Handbook of Medical Entomology is the outgrowth of a 
course of lectures along the lines of insect transmission and 
dissemination of diseases of man given by the senior author 
in the Department of Entomology of Cornell University during the 
past six years. More specifically it is an illustrated revision and 
elaboration of his “Notes on the Relation of Insects to Disease” 
published January, 1912. 

Its object is to afford a general survey of the field, and primarily 
to put the student of medicine and entomology in touch with the 
discoveries and theories which underlie some of the most important 
modern work in preventive medicine. At the same time the older 
phases of the subject—the consideration of poisonous and parasitic 
forms—have not been ignored. 

Considering the rapid shifts in viewpoint, and the development 
of the subject within recent years, the authors do not indulge in any 
hopes that the present text will exactly meet the needs of every 
one specializing in the field,—still less do they regard it as complete 
or final. The fact that the enormous literature of isolated articles is 
to be found principally in foreign periodicals and is therefore difficult 
of access to many American workers, has led the authors to hope 
that a summary of the important advances, in the form of a reference 
book may not prove unwelcome to physicians, sanitarians and 
working entomologists, and to teachers as a text supplementing 
lecture work in the subject. 

Lengthy as is the bibliography, it covers but a very small fraction 
of the important contributions to the subject. It will serve only to 
put those interested in touch with original sources and to open up 
the field. Of the more general works, special acknowledgment 
should be made to those of Banks, Brumpt, Castellani and Chalmers, 
Comstock, Hewitt, Howard, Manson, Mense, Neveau-Lemaire, 
Nuttall, and Stiles. 

To the many who have aided the authors in the years past, by 
suggestions and by sending specimens and other materials, sincerest 
thanks is tendered. This is especially due to their colleagues in 
the Department of Entomology of Cornell University, and to Pro¬ 
fessor Charles W. Howard, Dr. John Uri Lloyd, Mr. A. H. Ritchie, 
Dr. I. M. Unger, and Dr. Luzerne Coville. 


VI 


Preface 


They wish to express indebtedness to the authors and publishers 
who have so willingly given permission to use certain illustrations. 
Especially is this acknowledgment due to Professor John Henry 
Comstock, Dr. L. O. Howard, Dr. Graham-Smith, and Professor 
G. H. T. Nutt all. Professor Comstock not only authorized the use 
of departmental negatives by the late Professor M. V. Slingerland 
(credited as M. V. S.), but generously put at their disposal the illus¬ 
trations from the Manual for the Study of Insects and from 
the Spider Book. Figures 5 and 111 are from Peter’s “Der Arzt 
und die Heilkunft in der deutschen Vergangenheit.” It should be 
noted that on examining the original, it is found that Gottfried’s 
figure relates to an event antedating the typical epidemic of dancing 
mania. 


Cornell University, 
January, 1915. 


Wm. A. Riley. 

0. A. JOHANNSEN. 


ADDITIONS AND CORRECTIONS 

vi line 11, for Heilkunft read Heilkunst. 

18 line 2, for tarsi read tarsus. 

32 line 21, and legend under fig. 23, for C. (Conorhinus) 
abdominalis read Melanolestes abdominalis. 

47 legend under figure for 33c read 34. 

92 line 22 and 25, for sangiusugus read sanguisugus. 

116 legend under fig. 83, for Graham-Smith read Manson. 

136 line 10, from bottom, insert “ring” after “chitin”. 

137 line 3, for meditatunda read meditabunda. 

145 line 7, from bottom, for Rs read R s . 

158 line 20, for have read has. 

2T2 after the chapter heading insert “continued”. 

219 line 10, from bottom, for Cornohinus read Conorhinus. 

266 line 1, fig. 1581 refers to the female. 

272 line 5, insert “palpus” before “and leg”. 

281 line 6, for discodial read discoidal. 

281 last line, insert “from” before “the”. 

284 line 5, for “tubercle of” read “tubercle or”. 

305 lines 19, 28, 44, page 306 lines 1, 9, 22, 27, 30, page 307 line 7, 
page 309 lines 8, 11, for R 4 + 5 read 
309 legend under fig. 168 add Bureau of Entomology. 

312 line 36, for “near apex” read “of M r -f 2 .”. 

313 running headj for Muscidas read Muscoidea. 

314 line 29, for “distal section” read “distally M,+ 2 ”. 

315 legend under fig. 172, for Pseudopyrellia read Orthellia, 

for Lyperosia read Hasmatobia, for Umbana read urbana. 
323 and 325 legends under the figures, add “After Dr. J. H. 
Stokes”. 

328 line 7 from bottom for Apiochaeta read Aphiochaeta. 
































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CONTENTS 


CHAPTER I 

INTRODUCTION... 1-5 

Early suggestions regarding the transmission of disease by insects. 

The ways in which arthropods may affect the health of man. 

CHAPTER II 

ARTHROPODS WHICH ARE DIRECTLY POISONOUS. 6-56 

The Araneida, or Spiders. 

The tarantulas. Bird spiders. Spiders of the genus Latrodectus. Other 
venomous spiders. Summary. 

The Pedipalpida, or whip-scorpions. 

The Scorpionida, or true scorpions. 

The Solpugida, or solpugids. 

The Acarina, or mites and ticks. 

The Myriapoda, or centipedes and millipedes. 

The Hexapoda, or true insects. 

Piercing or biting insects poisonous to man. 

Hemiptera, or true bugs. 

The Notonectidee or back-swimmers. Belostomidae or giant water- 
bugs. Reduviidae, or assassin bugs. Other Hemiptera reported 
as poisonous to man. 

Diptera; the midges, mosquitoes and flies. 

Stinging insects. 

Apis mellifica, the honey bee. Other stinging forms. 

Nettling insects. 

Lepidoptera, or butterflies and moths. Relief from poisoning by nettling 
larvae. 

Vescicating insects and those possessing other poisons in their blood plasma. 
The blister beetles. Other cryptotoxic insects. 

CHAPTER III 

PARASITIC ARTHROPODS AFFECTING MAN. 57-130 

Acarina, or mites. 

The Trombidiidse, or harvest mites. 

The Ixodoidea, or ticks. 

Argasidae. Ixodidae. Treatment of tick bites. 

The mites. 

Dermanyssidae. Tarsonemidae. Sarcoptidae, the itch mites. Demode- 
cidae, the follicle mites. 

Hexapoda, or true insects. 

Siphunculata, or sucking lice. 

Hemiptera. 





VIII 


Contents 


The bed-bug. Other bed-bugs. 

Parasitic Diptera, or flies. 

Psychodidae, or moth flies. Phlebotominae. Culicidae, or mosquitoes. 
Simuliidae, or black-flies. Chironomidae, or midges. Tabanidae, or 
horse-flies. Leptidae or snipe-flies. Oestridas, or bot-flies. Muscidae, 
the stable-fly and others. 

Siphonaptera, or fleas. 

The fleas affecting man, the dog, cat, and rat. 

The true chiggers, or chigoes. 

CHAPTER IV 

ACCIDENTAL OR FACULTATIVE PARASITES. 131-143 

Acarina, or mites. 

Myriapoda, or centipedes and millipedes. 

Lepidopterous larvae. 

Coleoptera, or beetles. 

Dipterous larvae causing myiasis. 

Piophila casei, the cheese skipper. Chrysomyia macellaria, the screw- 
worm fly. Calliphorinae, the blue-bottles. Muscinae, the house or 
typhoid fly, and others. Anthomyiidas, the lesser house-fly and others. 
Sarcophagidae, the flesh-flies. 

CHAPTER V 

ARTHROPODS AS SIMPLE CARRIERS OF DISEASE. 144-163 

The house or typhoid fly as a carrier of disease. 

Stomoxys calcitrans, the stable-fly. 

Other arthropods which may serve as simple carriers of pathogenic organisms. 

CHAPTER VI 

ARTHROPODS AS DIRECT INOCULATORS OF DISEASE GERMS 164-174 

Some illustrations of direct inoculations of disease germs by arthropods. 

The r61e of fleas in the transmission of the plague. 

CHAPTER VII 

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC ORGAN¬ 
ISMS . 175-185 

Insects as intermediate hosts of tape-worms. 

Arthropods as intermediate hosts of nematode worms. Filariasis and mosqui¬ 
toes. 

Other nematode parasites of man and animals. 

CHAPTER VIII 

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PRO¬ 
TOZOA . 186-211 

Mosquitoes and malaria. 

Mosquitoes and yellow fever. 






Contents 


IX 


CHAPTER IX 

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PRO¬ 
TOZOA . 212-229 

Insects and trypanosomiases. 

Fleas and lice as carriers of Trypanosoma lewisi. 

Tsetse-flies and nagana. 

Tsetse-flies and sleeping sickness in man. 

South American trypanosomiasis. 

Leishmanioses and insects. 

Ticks and diseases of man and animals. 

Cattle tick and Texas fever. 

Ticks and Rocky Mountain Spotted fever of man. 


CHAPTER X 

ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTO¬ 
ZOA (Continued) . 230-240 

Arthropods and Spirochaetoses of man and animals. 

African relapsing fever of man. 

European relapsing fever. 

North African relapsing fever of man. 

Other types of relapsing fever of man. 

Spirochetosis of fowls. 

Other spirochaete diseases of animals. 

Typhus fever and lice. 

CHAPTER XI 

SOME POSSIBLE, BUT IMPERFECTLY KNOWN CASES OF 

ARTHROPOD TRANSMISSION OF DISEASE . 241-256 

Infantile paralysis, or acute anterior poliomyelitis. 

Pellagra. Leprosy. Verruga peruviana. Cancer. 


CHAPTER XII 

KEYS TO THE ARTHROPODS NOXIOUS TO MAN . 

Crustacea. 

Myriapoda, or centipedes and millipedes. 

Arachnida (Orders of). 

Acarina or ticks. 

Hexapoda (Insecta). 

Siphunculata and Hcmiptera (lice and true bugs). 

Diptera (mosquitoes, midges, and flies). 

Siphonaptera (fleas). 

APPENDIX 

Hydrocyanic acid gas against household insects. 

Proportion of ingredients. A single room as an example, 
large house. Precautions. 

Lesions produced by the bite of the black-fly. 

BIBLIOGRAPHY . 

INDEX . 


257-317 


. 318-320 

Fumigating a 

. 321-326 

. 327-340 

. 341-348 













CHAPTER I. 


INTRODUCTION 

EARLY SUGGESTIONS REGARDING THE TRANSMISSION OF DISEASE 

BY INSECTS 

Until very recent years insects and their allies have been considered 
as of economic importance merely in so far as they are an annoyance 
or direct menace to man, or his flocks and herds, or are injurious to 
his crops. It is only within the past fifteen years that there has 
sprung into prominence the knowledge that in another and much more 
insiduous manner, they may be the enemy of mankind, that they 
may be among the most important of the disseminators of disease. 
In this brief period, such knowledge has completely revolutionized 
our methods of control of certain diseases, and has become an import¬ 
ant weapon in the fight for the conservation of health. 

It is nowhere truer than in the case under consideration that how¬ 
ever abrupt may be their coming into prominence, great move¬ 
ments and great discoveries do not arise suddenly. Centuries ago 
there was suggested the possibility that insects were concerned with 
the spread of disease, and from time to time there have appeared keen 
suggestions and logical hypotheses along this line, that lead us to 
marvel that the establishment of the truths should have been so long 
delayed. 

One of the earliest of these references is by the Italian physician, 
Mercurialis, who lived from 1530 to 1607, during a period when 
Europe was being ravaged by the dread “black death”, or plague. 
Concerning its transmission he wrote: “There can be no doubt that 
flies feed on the internal secretions of the diseased and dying, then, 
flying away, they deposit their excretions on the food in neighboring 
dwellings, and persons who eat of it are thus infected.” 

It would be difficult to formulate more clearly this aspect of the 
facts as we know them to-day, though it must always be borne in 
mind that we are prone to interpret such statements in the light of 
present-day knowledge. Mercurialis had no conception of the animate 
nature of contagion, and his statement was little more than a lucky 
guess. 

Much more worthy of consideration is the approval which was 
given to his view by the German Jesuit, Athanasius Kircher in 1658. 


2 


Introduction 


One cannot read carefully his works without believing that long 
before Leeuwenhook’s discovery, Kircher had seen the larger species of 
bacteria. Moreover, he attributed the production of disease to these 
organisms and formulated, vaguely, to be sure, a theory of the animate 
nature of contagion. It has taken two and a half centuries to 
accumulate the facts to prove his hypothesis. 

The theory of Mercurialis was not wholly lost sight of, for in the 
medical literature of the eighteenth century there are scattered 
references to flies as carriers of disease. Such a view seems even to 
have been more or less popularly accepted, in some cases. Gudger 
(1910), has pointed out that, as far back as 1769, Edward Bancroft, 
in “An Essay on the Natural History of Guiana in South America,” 
wrote concerning the contagious skin-disease known as “Yaws”: 
“It is usually believed that this disorder is communicated by the flies 
who have been feasting on a diseased object, to those persons who have 
sores, or scratches, which are uncovered; and from many observa¬ 
tions, I think this is not improbable, as none ever receive this disorder 
whose skins are whole.” 

Approaching more closely the present epoch, we find that in 1848, 
Dr. Josiah Nott, of Mobile, Alabama, published a remarkable 
article on the cause of yellow fever, in which he presented “reasons for 
supposing its specific cause to exist in some form of insect life.” 
As a matter of fact, the bearing of Nott’s work on present day ideas 
of the insect transmission of disease has been very curiously overrated. 
The common interpretation of his theory has been deduced from a few 
isolated sentences, but his argument appears quite differently when 
the entire article is studied. It must be remembered that he wrote at 
a period before the epoch-making discoveries of Pasteur and before 
the recognition of micro-organisms as factors in the cause of disease. 
His article is a masterly refutation of the theory of “malarial” origin 
of “all the fevers of hot climates,” but he uses the term “insect” as 
applicable to the lower forms of life, and specific references to “mos¬ 
quitoes,” “aphids,” “cotton-worms,” and others, are merely in the 
way of similes. 

But, while Nott’s ideas regarding the relation of insects to yellow 
fever were vague and indefinite, it was almost contemporaneously 
that the French physician, Louis Daniel Beauperthuy argued in the 
most explicit possible manner, that yellow fever and various others 
are transmitted by mosquitoes. In the light of the data which were 
available when he wrote, in 1853, it is not surprising that he erred by 




Early Suggestions 


3 


thinking that the source of the virus was decomposing matter which 
the mosquito took up and accidentally inoculated into man. Beau- 
perthuy not only discussed the role of mosquitoes in the transmission 
of disease, but he taught, less clearly, that house-flies scatter patho¬ 
genic organisms. It seems that Boyce (1909) who quotes extensively 
from this pioneer work, does not go too far when he says “It is Dr. 
Beauperthuy whom we must regard as the father of the doctrine of 
insect-borne disease.” 

In this connection, mention must be made of the scholarly article 
by the American physician, A. F. A. King who, in 1883, brought 
together an all but conclusive mass of argument in support of his 
belief that malaria was caused by mosquitoes. At about the same 
time, Finley, of Havana, was forcefully presenting his view that the 
mosquito played the chief r 61 e in the spread of yellow fever. 

To enter more fully into the general historical discussion is beyond 
the scope of this book. We shall have occasion to make more 
explicit references in considering various insect-borne diseases. 
Enough has been said here to emphasize that the recognition of 
insects as factors in the spread of disease was long presaged, and that 
there were not wanting keen thinkers who, with a background of 
present-day conceptions of the nature of disease, might have been in 
the front rank of investigators along these lines. 

THE WAYS IN WHICH ARTHROPODS MAY AFFECT THE HEALTH 

OF MAN 

When we consider the ways in which insects and their allies may 
affect the health of man, we find that we may treat them under three 
main groups: 

A. They may be directly poisonous. Such, for example, are the 
scorpions, certain spiders and mites, some of the predaceous bugs, 
and stinging insects. Even such forms as the mosquito deserve 
some consideration from this viewpoint. 

B. They may be parasitic, living more or less permanently on 
or in the body and deriving their sustenance from it. 

Of the parasitic arthropods we may distinguish, first, the true 
parasites, those which have adopted and become confirmed in the 
parasitic habit. Such are the itch mites, the lice, fleas, and the 
majority of the forms to be considered as parasitic. 

In addition to these, we may distinguish a group of accidental, or 
facultative parasites, species which are normally free-living, feeding on 


4 


Introduction 


decaying substances, but which when accidentally introduced into 
the alimentary canal or other cavities of man, may exist there 
for a greater or less period. For example, certain fly larvas, or mag¬ 
gots, normally feeding in putrifying meat, have been known to occur 
as accidental or facultative parasites in the stomach of man. 

C. Finally, and most important, arthropods may be trans¬ 
mitters and disseminators of disease. In this capacity they may 
function in one of three ways; as simple carriers , as direct inoculators , 
or as essential hosts of disease germs. 

As simple carriers, they may, in a wholly incidental manner, 
transport from the diseased to the healthy, or from filth to food, 
pathogenic germs which cling to their bodies or appendages. Such, 
for instance, is the relation of the house-fly to the dissemination of 
typhoid. 

As direct inoculators, biting or piercing species may take up from 
a diseased man or animal, germs which, clinging to the mouth parts, 
are inoculated directly into the blood of the insect’s next victim. It 
it thus that horse-flies may occasionally transmit anthrax. Similarly, 
species of spiders and other forms which are ordinarily perfectly 
harmless, may accidentally convey and inoculate pyogenic bacteria. 

It is as essential hosts of disease germs that arthropods play their 
most important role. In such cases an essential part of the life cycle 
of the pathogenic organism is undergone in the insect. In other 
words, without the arthropod host the disease-producing organism 
cannot complete its development. As illustrations may be cited the 
relation of the Anopheles mosquito to the malarial parasite, and the 
relation of the cattle tick to Texas fever. 

A little consideration will show that this is the most important of 
the group. Typhoid fever is carried by water or by contaminated 
milk, and in various other ways, as well as by the house-fly. Kill all 
the house-flies and typhoid would still exist. On the other hand, 
malaria is carried only by the mosquito, because an essential part of 
the development of the malarial parasite is undergone in this insect. 
Exterminate all of the mosquitoes of certain species and the dis¬ 
semination of human malaria is absolutely prevented. 

Once an arthropod becomes an essential host for a given parasite 
it may disseminate infection in three different ways: 

i. By infecting man or animals who ingest it. It is thus, for 
example, that man, dog, or cat, becomes infected with the double- 
pored dog tapeworm, Dipylidium caninwn. The cysticercoid stage 



Arthropods and Man 


5 


occurs in the dog louse, or in the dog or cat fleas, and by accidentally 
ingesting the infested insect the vertebrate becomes infested. Simi¬ 
larly, Hymenolepis diminuta, a common tapeworm of rats and mice, 
and occasional in man, undergoes part of its life cycle in various meal- 
infesting insects, and is accidentally taken up by its definitive host. 
It is very probable that man becomes infested- with Dracunculus 
( Filaria ) medinensis through swallowing in drinking water, the 
crustacean, Cyclops, containing the larvae of this worm. 

2. By infecting man or animals on whose skin or mucous mem¬ 
branes the insect host may be crushed or may deposit its excrement. 
The pathogenic organism may then actively penetrate, or may be 
inoculated by scratching. The causative organism of typhus fever 
is thus transmitted by the body louse. 

3. By direct inoculation by its bite, the insect host may transfer 
the parasite which has undergone development within it. The 
malarial parasite is thus transferred by mosquitoes; the Texas fever 
parasite by cattle ticks. 


CHAPTER II. 


ARTHROPODS WHICH ARE DIRECTLY POISONOUS 

Of all the myriads of insects and related forms, a very few are of 
direct use to man, some few others have forced his approbation on 
account of their wonderful beauty, but the great hordes of them are 
loathed or regarded as directly dangerous. As a matter of fact, only 
a very small number are in the slightest degree poisonous to man or 
to the higher animals. The result is that entomologists and lovers 
of nature, intent upon dissipating the foolish dread of insects, are 
sometimes inclined to go to the extreme of discrediting all statements 
of serious injury from the bites or stings of any species. 

Nevertheless, it must not be overlooked that poisonous forms do 
exist, and they must receive attention in a consideration of the ways 
in which arthropods may affect the health of man. Moreover, it 
must be recognized that “what is one man’s meat, is another man’s 
poison,” and that in considering the possibilities of injury we must not 
ignore individual idiosyncrasies. Just as certain individuals may be 
poisoned by what, for others are common articles'of food, so some 
persons may be abnormally susceptible to insect poison. Thus, the 
poison of a bee sting may be of varying severity, but there are individ¬ 
uals who are made seriously sick by a single sting, regardless of the 
point of entry. Some individuals scarcely notice a mosquito bite, 
others find it very painful, and so illustrations of this difference in 
individuals might be multiplied. 

In considering the poisonous arthropods, we shall take them up by 
groups. The reader who is unacquainted with the systematic rela¬ 
tionship of insects and their allies is referred to Chapter XII. No 
attempt will be made to make the lists under the various headings 
exhaustive, but typical forms will be discussed. 

ARANEIDA OR SPIDERS 

Of all the arthropods there are none which are more universally 
feared than are the spiders. It is commonly supposed that the 
majority, if not all the species are poisonous and that they are aggres¬ 
sive enemies of man and the higher animals, as well as of lower forms. 

That they really secrete a poison may be readily inferred from the 
effect of their bite upon insects and other small forms. Moreover, 


Araneida or Spiders 


7 



Head of a spider showing 
poison gland ( c ) and its re¬ 
lation to the chelicera (a). 


the presence of definite and well-developed poison glands can easily 
be shown. They occur as a pair of pouches (fig. i) lying within the 
cephalothorax and connected by a delicate 
duct with a pore on the claw of the chelicera, 
or so-called “mandible” on the convex surface 
of the claw in such a position that it is not 
plugged and closed by the flesh of the victim. 

The glands may be demonstrated by slowly 
and carefully twisting off a chelicera and 
pushing aside the stumps of muscles at its 
base. By exercising care, the chitinous wall 
of the chelicera and its claw may be broken 
away and the duct traced from the gland to its outlet. The inner 
lining of the sac is constituted by a highly developed glandular 
epithelium, supported by a basement membrane of connective 
tissue and covered by a muscular layer, (fig. 2). The muscles, which 
are striated, are spirally arranged (fig. 1), and are doubtless under 
control of the spider, so that the amount of poison to be injected into 
a wound may be varied. 

The poison itself, according to Kobert (1901), is a clear, colorless 
fluid, of oily consistency, acid reaction, and very bitter taste. After 
the spider has bitten two or three times, its supply is exhausted and 
therefore, as in the case of snakes, the poison of the bite decreases 
quickly with use, until it is null. To what extent the content of the 
poison sacs may contain blood serum or, at least, active principles of 
serum, in addition to a specific poison formed by the poison glands 
themselves, Kobert regards as an open question. He believes that 
the acid part of the poison, if really present, 
is formed by the glands and that, 
in the case of some spiders, the 
ferment-like, or better, active 
toxine, comes from the blood. 

But there is a wide difference 
between a poison which may kill 
an insect and one which is harm¬ 
ful to men. Certain it is that 
there is no lack of popular belief 
and newspaper records of fatal 
cases, but the evidence regarding the possibility of fatal or even vein- 
serious results for man is most contradictory. For some years, 
we have attempted to trace the more circumstantial newspaper 




3. Chelicera of 
spider. 


Section through a venom 
gland of Latrodectus 
13 -guttatus showing 
the peritoneal, muscu¬ 
lar and epithelial layers. 
After Bordas. 




8 


Poisonous Arthropods 


accounts, which have come to our notice, of injury by North 
American species. The results have served, mainly, to empha¬ 
size the straits to which reporters are sometimes driven when 
there is a dearth of news. The accounts are usually vague and lack¬ 
ing in any definite clue for locating the supposed victim. In the 
comparatively few cases where the patient, or his physician, could 
be located, there was either no claim that the injury wa% due to 
spider venom, or there was no evidence to support the belief. 
Rarely, there was evidence that a secondary blood poisoning, such 
as might be brought about by the prick of a pin, or by any mechani¬ 
cal injury, had followed the bite of a spider. Such instances have 

no bearing on the question of the 
venomous nature of these forms. 

The extreme to which unreason¬ 
able fear of the bites of spiders 
influenced the popular mind was 
evidenced by the accepted explana¬ 
tion of the remarkable dancing 
mania, or tarantism, of Italy during 
the Middle Ages. This was a ner¬ 
vous disorder, supposed to be due 
to the bite of a spider, the European 
tarantula (fig. 4), though it was 
also, at times, attributed to the 

4. The Italian tarantula (Lycosa tarantula), bite of the SCOrpion. In its tvpical 

form, it was characterized by so 
great a sensibility to music that under its influence the victims 
indulged in the wildest and most frenzied dancing, until they sank 
to the ground utterly exhausted and almost lifeless. The profuse 
perspiring resulting from these exertions was supposed to be the 
only efficacious remedy for the disease. Certain forms of music 
were regarded as of especial value in treating this tarantism, and 
hence the name of “ tarantella” was applied to them. Our frontis¬ 
piece, taken from Athanasius Kircher’s Magnes sive de Arte Magnetica, 
1643 ed., represents the most commonly implicated spider and illus¬ 
trates some of what Fabre has aptly designated as “medical 
choreography.” 

The disease was, in reality, a form of hysteria, spreading by sym¬ 
pathy until whole communities were involved, and was paralleled by 
the outbreaks of the so-called St. Vitus’s or St. John’s dance, which 




Araneida or Spiders 


9 


swept Germany at about the same time (fig. 5). The evidence that 
the spider was the cause of the first is about as conclusive as is that 
of the demoniacal origin of the latter. The true explanation of the 
outbreaks is doubtless to be found in the depleted physical and mental 
condition of the people, resulting from the wars and the frightful 
plagues which devastated all Europe previous to, and during these 
times. An interesting discussion of these aspects of the question is to 
be found in Hecker. 



5 . Dancing mania. Illustration from Johann Ludwig Gottfried's Chronik. 1632. 


So gross has been the exaggeration and so baseless the popular fear 
regarding spiders that entomologists have been inclined to discredit 
all accounts of serious injury from their bites. Not only have the 
most circumstantial of newspaper accounts proved to be without 
foundation but there are on record a number of cases where the bite 
of many of the commoner species have been intentionally provoked 
and where the effect has been insignificant. Some years ago the 
senior author personally experimented with a number of the largest of 
our northern species, and with unexpected results. The first surprise 
was that the spiders were very unwilling to bite and that it required a 
considerable effort to get them to attempt to do so. In the second 






















IO 


Poisonous Arthropods 


place, most of those experimented with were unable to pierce the skin 
of the palm or the back of the hand, but had to be applied to the thin 
skin between the fingers before they were able to draw blood. Unfor¬ 
tunately, no special attempt was made to determine, at the time, the 
species experimented with, but among them were Theridion tepi- 
dariorum, Miranda aurantia (Argiopa ), Metargiope trifasciata, Marxia 
stellata, Aranea trifolium, Misumena vatia, and Agelena ncevia. In 
no case was the bite more severe than a pin prick and though in some 
cases the sensation seemed to last longer, it was probably due to the 
fact that the mind was intent upon the experiment. 

Similar experiments were carried out by Blackwell (1855), who 
believed that in the case of insects bitten, death did not result any 



6. An American tarantula (Eurypelma hentzii). Natural size. After Comstock 

more promptly than it would have from a purely mechanical injury of 
equal extent. He was inclined to regard all accounts of serious 
injury to man as baseless. The question cannot be so summarily 
dismissed, and we shall now consider some of the groups which have 
been more explicitly implicated. 

The Tarantulas. — In popular usage, the term “ tarantula ” is 
loosely applied to any one of a number of large spiders. The famous 
tarantulas of southern Europe, whose bites were supposed to cause the 
dancing mania, were Lycosidae, or wolf-spiders. Though various 
species of this group were doubtless so designated, the one which 
seems to have been most implicated was Lycosa tarantula (L.), 
(fig. 4). On the other hand, in this country, though there are many 
Lycosidae, the term “tarantula” has been applied to members of the 
superfamily Avicularoidea (fig. 6), including the bird-spiders. 

Of the Old World Lycosidae there is no doubt that several species 
were implicated as the supposed cause of the tarantism. In fact, as 
we have already noted, the blame was sometimes attached to a scor- 


The Tarantulas 


11 

pion. However, there seems to be no doubt that most of the accounts 
refer to the spider known as Lycosa tarantula. 

There is no need to enter into further details here regarding the 
supposed virulence of these forms, popular and the older medical 
literature abound in circumstantial accounts of the terrible effects of 
the bite. Fortunately, there is direct experimental evidence which 
bears on the question. 

Fabre induced a common south European wolf-spider, Lycosa 
narbonensis, to bite the leg of a young sparrow, ready to leave the 
nest. The leg seemed paralyzed as a result of the bite, and though 
the bird seemed lively and clamored for food the next day, on the 
third day it died. A mole, bitten on the nose, succumbed after thirty- 
six hours. From these experiments Fabre seemed justified in his 
conclusion that the bite of this spider is not an accident which man 
can afford to treat lightly. Unfortunately, there is nothing in the 
experiments, or in the symptoms detailed, to exclude the probability 
that the death of the animals was the result of secondary infection. 

As far back as 1693, as we learn from the valuable account of 
Robert, (1901), the Italian physician, Sanguinetti allowed himself to 
be bitten on the arm by two tarantulas, in the presence of witnesses. 
The sensation was equivalent to that from an ant or a mosquito bite 
and there were no other phenomena the first day. On the second day 
the wound was inflamed and there was slight ulceration. It is clear 
that these later symptoms were due to a secondary infection. These 
experiments have been repeated by various observers, among whom 
may be mentioned Leon Dufour, Josef Erker and Heinzel, and with 
the similar conclusion that the bite of the Italian tarantula ordinarily 
causes no severe symptoms. In this conclusion, Robert, though 
firmly convinced of the poisonous nature of some spiders, coincides. 
He also believes that striking symptoms may be simulated or arti¬ 
ficially induced by patients in order to attract interest, or because 
they have been assured that the bite, under all circumstances, caused 
tarantism. 

The so-called Russian tarantula, Trochosa singoriensis (fig. 7), is 
much larger than the Italian species, and is much feared. Robert 
carried out a series of careful experiments with this species and his 
results have such an important bearing on the question of the venom¬ 
ous nature of the tarantula that we quote his summary. Experi¬ 
menting first on nearly a hundred living specimens of Trochosa 
singoriensis from Crimea he says that: 


12 


Poisonous Arthropods 


“The tarantulas, no matter how often they were placed on the 
skin, handled, and irritated, could not be induced to bite either myself, 
the janitor, or the ordinary experimental animals. The objection 
that the tarantulas were weak and indifferent cannot stand, for as 
soon as I placed two of them on the shaved skin of a rabbit, instead of 
an attack on the animal, there began a furious battle between the 
two spiders, which did not cease until one of the two was killed.” 

“Since the spiders would not 
bite, I carefully ground up the 
fresh animals in physiological 
salt solution, preparing an extract 
which must have contained, in 
solution, all of the poisonous 
substance of their bodies. While 
in the case of Latrodectus, as we 
shall see, less than one specimen 
sufficed to yield an active extract, 
I have injected the filtered extract 
of six fresh Russian tarantulas, 
of which each one was much 
heavier than an average Latro¬ 
dectus , subcutaneously and into 
the jugular vein of various cats 
without the animals dying or 
showing any special symptoms. 
On the basis of my experiments I can therefore only say that the 
quantity of the poison soluble in physiological salt solution, even 
when the spiders are perfectly fresh and well nourished, is very 
insignificant. That the poison of the Russian tarantula is not 
soluble in physiological salt solution, is exceedingly improbable. 
Moreover, I have prepared alcoholic extracts and was unable to 
find them active. Since the Russian spider exceeds the Italian in 
size and in intensity of the bite, it seems very improbable to me that 
the pharmacological test of the Italian tarantula would yield 
essentially other results than those from the Russian species.” 

To the Avicularoidea belong the largest and most formidable 
appearing of the spiders and it is not strange that in the New World 
they have fallen heir to the bad reputation, as well as to the name of 
the tarantula of Europe. In this country they occur only in the 
South or in the far West, but occasionally living specimens are brought 







The Tarantulas 


*3 


to our northern ports in shipments of bananas and other tropical 
produce, and are the source of much alarm. It should be mentioned, 
however, that the large spider most frequently found under such cir¬ 
cumstances is not a tarantula at all, but one of the Heteropodidae, or 
giant crab-spiders, (fig. 8). 

In spite of their prominence and the fear which they arouse there 
are few accurate data regarding these American tarantulas. It has 



8. The giant crab-spider or banana spider (Heteropoda venatoria). 

Natural size. After Comstock. 

often been shown experimentally that they can kill small birds and 
mammals, though it is doubtful if these form the normal prey of any 
of the species, as has been claimed. There is no question but that 
the mere mechanical injury which they may inflict, and the consequent 
chances of secondary infection, justify, in part, their bad reputation. 
In addition to the injury from their bite, it is claimed that the body 
hairs of several of the South American species are readily detached 
and are urticating. 

Recently, Phisalix (1912) has made a study of the physiological 
effects of the venom of two Avicularoidea, Phormictopus carcerides 
Pocock, from Haiti and Cteniza sauvagei Rossi, from Corsica. The 
glands were removed aseptieally and ground up with fine, sterilized 
sand in distilled water. The resultant liquid was somewhat viscid, 
colorless, and feebly alkaline. Injected into sparrows and mice the 
















14 


Poisonous Arthropods 


extract of Phormictopus proved very actively poisonous, that from a 
single spider being sufficient to kill ten sparrows or twenty-mice. It 
manifested itself first and, above all, as a narcotic, slightly lowering 
the temperature and paralyzing the respiration. Muscular and 
cardiac weakening, loss of general sensibility, and the disappearance 
of reflexes did not occur until near the end. The extract from Cteniza 
was less active and, curiously enough, the comparative effect on 
sparrows and on mice was just reversed. 

Spiders of the Genus Latrodectus. —While most of the popular 

accounts of evil effects from the bites of spiders will not stand investi¬ 
gation, it is a significant fact that, the world over, the best authentica¬ 
ted records refer to a group of small and comparatively insignificant 
spiders belonging to the genus Latrodectus, of the family Theridiidae. 
The dread “ Malmigniatte” of Corsica and South Europe, the “Kara- 
kurte” of southeastern Russia, the “Katipo” of New Zealand the 
“Mena-vodi” and “ Vaneoho” of Madagascar, hnd our own Latrodectus 
mactans, all belong to this genus, and concerning all of these the most 
circumstantial accounts of their venomous nature are given. These 
accounts are not mere fantastic stories by uneducated natives but in 
many cases are reports from thoroughly trained medical men. 

The symptoms produced are general, rather than local. As 
summarized by Robert (1901) from a study of twenty-two cases 
treated in 1888, in the Kherson (Russia) Government Hospital and 
Berislaw (Kherson) District Hospital the typical case, aside from 
complications, exhibits the following symptoms. The victim sud¬ 
denly feels the bite, like the sting of a bee. Swelling of the barely 
reddened spot seldom follows. The shooting pains, which quickly 
set in, are not manifested at the point of injury but localized at the 
joints of the lower limb and in the region of the hip. The severity 
of the pain forces the victim to the hospital, in spite of the fact that 
they otherwise have a great abhorrence of it. The patient is unable 
to reach the hospital afoot, or, at least, not without help, for there is 
usually inability to walk. The patient, even if he has ridden, reaches 
the hospital covered with cold sweat and continues to perspire for a 
considerable period. His expression indicates great suffering. The 
respiration may be somewhat dyspnoeic, and a feeling of oppression 
in the region of the heart is common. There is great aversion to 
solid food, but increasing thirst for milk and tea. Retention of 
urine, and constipation occur. Cathartics and, at night, strong 


Spiders of the Genus Latrodectus 


15 


narcotics are desired. Warm baths give great relief. After three 
days, there is marked improvement and usually the patient is dis¬ 
missed after the fifth. This summary of symptoms agrees well with 
other trustworthy records. 

It would seem, then, that Riley and Howard (1889), who discussed 
a number of accounts in the entomological literature, were fully 
justified in their statement that “It must be admitted that certain 
spiders of the genus Latrodectus have the power to inflict poisonous 
bites, which may (probably exceptionally and depending upon excep¬ 
tional conditions) bring about the death of a human being.” 

And yet, until recently the evidence bearing on the question has 
been most conflicting. The eminent arachnologist, Lucas, (1843) 
states that he himself, had been repeatedly bitten by the Malmigniatte 
without any bad effects. Dr. Marx, in 1890, gave before the Ento¬ 
mological Society of Washington, an account of a series of experiments 
to determine whether the bite of Latrodectus mactans is poisonous or 
not. He described the poison glands as remarkably small* and stated 
that he had introduced the poison in various ways into guinea-pigs 
and rabbits without obtaining any satisfactory results. Obviously, 
carefully conducted experiments with the supposed venom were 
needed and fortunately they have been carried out in the greatest 
detail by Robert (1901). 

This investigator pointed out that there were two factors which 
might account for the discrepancies in the earlier experiments. In 
the first place, the poison of spiders, as of snakes, might be so ex¬ 
hausted after two or three bites that further bites, following directly, 
might be without visible effect. Secondly, the application of the 
poison by means of the bite, is exceedingly inexact, since even after 
the most careful selection of the point of application, the poison might 
in one instance enter a little vein or lymph vessel, and in another case 
fail to do so. Besides, there would always remain an incalculable and 
very large amount externally, in the nonabsorptive epithelium. 
While all of these factors enter into the question of the effect of the 
bite in specific instances, they must be as nearly as possible obviated 
in considering the question of whether the spiders really secrete a 
venom harmful to man. 

*This is diametrically opposed to the findings of Bordas (1905) in the case 
of the European Latrodectus ij-guttatus, whose glands are “much larger than 
those of other spiders.” From a considerable comparative study, we should also 
unhesitatingly make this statement regarding the glands of our American species, 
L. mactans. 



i6 


Poisonous Arthropods 


Kobert therefore sought to prepare extracts which would contain 
the active principles of the poison and which could be injected in 
definite quantities directly into the blood of the experimental animal. 
For this purpose various parts of the spiders were rubbed up in a mor¬ 
tar with distilled water, or physiological salt solution, allowed to 
stand for an hour, filtered, and then carefully washed, by adding water 
drop by drop for twenty-four hours. The filtrate and the wash- 
water were then united, well mixed and, if necessary, cleared by cen¬ 
trifuging or by exposure to cold. The mixture was again filtered, 
measured, and used, in part, for injection and, in part, for the deter¬ 
mination of the organic materials. 

Such an extract was prepared from the cephalothoraces of eight 
dried specimens of the Russian Latrodectus and three cubic centimeters 
of this, containing 4.29 mg. of organic material, were injected into 
the jugular vein of a cat weighing 2450 grams. The previously very 
active animal was paralyzed and lay in whatever position it was 
placed. The sensibility of the skin of the extremities and the rump 
was so reduced that there was no reaction from cutting or sticking. 
There quickly followed dyspnoea, convulsions, paralysis of the 
respiratory muscles and of the heart. I11 twenty-eight minutes the 
cat was dead, after having exhibited exactly the symptoms observed 
in severe cases of poisoning of man from the bite of this spider. 

These experiments were continued on cats, dogs, guinea pigs and 
various other animals. Not only extracts from the cephalothorax, 
but from other parts of the body, from newly hatched spiders, and 
from the eggs were used and all showed a similar virulence. Every 
effort was made to avoid sources of error and the experiments, con¬ 
ducted by such a recognized authority in the field of toxicology, must 
be accepted as conclusively showing that this spider and, presumably, 
other species of the genus Latrodectus against which the clinical evi¬ 
dence is quite parallel, possess a poison which paralyzes the heart and 
central nervous system, with or without preliminary stimulus of the 
motor center. If the quantity of the poison which comes into direct 
contact with the blood is large, there may occur haemolysis and 
thrombosis of the vessels. 

On ihe other hand, check experiments were carried out, using 
similar extracts of many common European spiders of the genera 
Tegenaria, Drassus, Agelena, Eucharia and Argyroneta, as well as 
the Russian tarantula, Lycosa singoriensis. In no other case was the 
effect on experimental animals comparable to the Latrodectus extract- 


Spiders of the Genus Latrodectus 


i7 


Robert concludes that in its chemical nature the poison is neither 
an alkaloid, nor a glycoside, nor an acid, but a toxalbumen, or poison¬ 
ous enzyme which is very similar to certain other animal poisons, 
notably that of the scorpion. 



9 . Latrodectus mactans; (a) female, x 3; ( b ) venter of female; (e) dorsum of male. 

After Comstock. 

The genus Latrodectus is represented in the United States by at 
least two species, L. mactans and L. geometricus. Concerning L. 
mactans there are very circumstantial accounts of serious injury and 
even death in man*. Latrodectus mactans is coal black, marked with 
red or yellow or both. It has eight eyes, which arc dissimilar in 

*Dr. E. H. Coleman (Kellogg, 1915) has demonstrated its virulence by a series 
of experiments comparable with those of Kobert. 

















i8 


Poisonous Arthropods 


color and are distinctly in front of the middle of the thorax, the 
lateral eyes of each side widely separate. The tarsi of the fourth 
pair of legs has a number of curved setae in a single series. It has on 
the ventral side of its abdomen an hour-glass shaped spot. The full- 
grown female is about half an inch in length. Its globose abdomen is 
usually marked with one or more red spots dorsally along the middle 
line. The male is about half as long but has in addition to the dorsal 
spots, four pairs of stripes along the sides. Immature females 
resemble the male in coloring (fig. 9). 

Regarding the distribution of Latrodectus mactans, Comstock 
states that: “Although it is essentially a Southern species, it occurs 
in Indiana, Ohio, Pennsylvania, New Hampshire, and doubtless other 
of the Northern States.” L. geometricus has been reported from 
California. 

Other Venomous Spiders —While conclusive evidence regarding 
the venomous nature of spiders is meager and relates almost wholly 
to that of the genus Latrodectus, the group is a large one and we are 
not justified in dismissing arbitrarily, all accounts of injury from their 
bites. Several species stand out as especially needing more detailed 
investigation. 

Chiracanthium nutrix is a common European species of the family 
Clubionidse, concerning which there is much conflicting testimony. 
Among the reports are two by distinguished scientists whose accounts 
of personal experiences cannot be ignored. A. Forel allowed a spider 
of this species to bite him and not only was the pain extreme, but the 
general symptoms were so severe that he had to be helped to his 
house. The distinguished arachnologist, Bertkau reports that he, 
himself, was bitten and that an extreme, burning pain spread almost 
instantaneously over the arm and into the breast. There were slight 
chills the same day and throbbing pain at the wound lasted for days. 
While this particular species is not found in the United States, there 
are two other representatives of the genus and it is possible that they 
possess the same properties. We are unaware of any direct experi¬ 
mental work on the poison. 

Epeira diadema, of Europe, belongs to a wholly different group, 
that of the orb-weavers, but has long been reputed venomous. Robert 
was able to prepare from it an extract whose effects were very similar 
to that prepared from Latrodectus, though feebler in its action. Under 
ordinary circumstances this spider is unable to pierce the skin of man 


Other Venomous Spiders 


iQ 


and though Robert’s results seem conclusive, the spider is little to 
be feared. 

Phidippus audax ( P. tripunctatus) is one of our largest Attids, 
or jumping spiders. The late Dr. O. Lugger describes a case of severe 
poisoning from the bite of this spider and though details are lacking, 
it is quite possible that this and other large species of the same group, 
which stalk their prey, may possess a more active poison than that of 
web-building species. 


Summary It is clearly established that our common spiders are 
not to be feared and that the stories regarding their virulence are 



10 . A whip-scorpion (Mastigoproctus giganteus). 
Half natural size. After Comstock. 


and may even cause death in man 

THE PEDIPALPIDA OR 


almost wholly without founda¬ 
tion. On the other hand, the 
chances of secondary infection 
from the bites of some of the 
more powerful species are not 
to be ignored. 

Probably all species possess 
a toxin secreted by the poison 
gland, virulent for insects and 
other normal prey of the 
spiders, but with little or no 
effect on man. 

There are a very few species, 
notably of the genus Latrodectus , 
and possibly including the Euro¬ 
pean Chiracantkium nutrix and 
Epeira diadema, which possess, 
in addition, a toxalbumen 
derived from the general body 
tissue, which is of great virulence 
and the higher animals. 

WHIP-SCORPIONS 


The tailed whip-scorpions, belonging to the family Thelyphonidae, 
are represented in the United States by the giant whip-scorpion 
Mastigoproctus giganteus (fig. 10), which is common in Florida, Texas 
and some other parts of the South. In Florida, it is locally known as 
the “grampus” or “mule-killer” and is very greatly feared. There is 
no evidence that these fears have any foundation, and Dr. Marx 
states that there is neither a poison gland nor a pore in the claw of the 
chelicera. 


20 


Poisonous Arthropods 

THE SC 0 RPI 0 NIDA, OR TRUE SCORPIONS 


The true scorpions are widely distributed throughout warm coun¬ 
tries and everywhere bear an evil reputation. According to Comstock 
(1912), about a score of species occur in the Southern United States. 
These are comparatively small forms but in the tropics members of 
this group may reach a length of seven or eight inches. They are 
pre-eminently predaceous forms, which lie hidden during the day and 
seek their prey by night. 

The scorpions (fig. 11) possess large pedipalpi, terminated by 
strongly developed claws, or chelae. They may be distinguished from 
all other Arachnids by the fact that the dis¬ 
tinctly segmented abdomen is divided into a 
broad basal region of seven segments and a 
terminal, slender, tail-like division of five 
distinct segments. 

The last segment of the abdomen, or 
telson, terminates in a ventrally-directed, 
sharp spine, and contains a pair of highly 
developed poison glands. These glands open 
by two small pores near the tip of the spine. 
Most of the species when running carry the 
tip of the abdomen bent upward over the 
back, and the prey, caught and held by the 
pedipalpi, is stung by inserting the spine of 
the telson and allowing it to remain for a 
time in the wound. 

The glands themselves have been studied 
in Prionurus citrinus by Wilson (1904). 
He found that each gland is covered by a sheet of muscle on its 
mesal and dorsal aspects, which may be described as the compressor 
muscle. The muscle of each side is inserted by its edge along the 
ventral inner surface of the chitinous wall of the telson, close to the 
middle line, and by a broader insertion laterally. A layer of fine 
connective tissue completely envelops each gland and forms the 
basis upon which the secreting cells rest. The secreting epithelium 
is columnar; and apparently of three different types of cells. 

1. The most numerous have the appearance of mucous cells, 
resembling the goblet cells of columnar mucous membranes. The 
nucleus, surrounded by a small quantity of protoplasm staining with 
hematoxylin, lies close to the base of the cell. 



A true scorpion. 
Comstock. 


After 



The True Scorpions 


21 


2. Cells present in considerable numbers, the peripheral por¬ 
tions of which are filled with very numerous fine granules, staining 
with acid dyes such as methyl orange. 

3. Cells few in number, filled with very large granules, or ir¬ 
regular masses of a substance staining with hasmatoxylin. 

The poison, according to Robert (1893), is a limpid, acid-reacting 
fluid, soluble in water but insoluble in absolute alcohol and ether. 
There are few data relative to its chemical nature. Wilson (1901) 
states that a common Egyptian species, Buthus quinquestriatus, has 
a specific gravity of 1.092, and contains 20.3% of solids and 8.4% ash. 

The venom of different species appears to differ not only quantita¬ 
tively but qualitatively. The effects of the bite of the smaller species 
of the Southern United States may be painful but there is no satis¬ 
factory evidence that it is ever fatal. On the other hand, certain 
tropical species are exceedingly virulent and cases of death of man 
from the bite are common. 

In the case of Buthus quinquestriatus, Wilson (1904) found the 
symptoms in animals to be hypersecretion, salivation and lachryma- 
tion, especially marked, convulsions followed by prolonged mus¬ 
cular spasm; death from asphyxia. The temperature shows a 
slight, rarely considerable, rise. Rapid and considerable increase 
of blood-pressure (observed in dogs) is followed by a gradual fall with 
slowing of the heart-beat. The coagulability of the blood is not 
affected. 

An interesting phase of Wilson’s work was the experiments on 
desert mammals. The condition under which these animals exist 
must frequently bring them in contact with scorpions, and he found 
that they possess a degree of immunity to the venom sufficient at 
least to protect them from the fatal effects of the sting. 

As far as concerns its effect on man, Wilson found that much 
depended upon the age. As high as 60 per cent of the cases of 
children under five, resulted fatally. Caroroz (1865), states that in a 
Mexican state of 15,000 inhabitants, the scorpions were so abundant 
and so much feared that the authorities offered a bounty for their 
destruction. A result was a large number of fatalities, over two 
hundred per year. Most of the victims were children who had 
attempted to collect the scorpions. 

The treatment usually employed in the case of bites by the more 
poisonous forms is similar to that for the bite of venomous snakes. 
First, a tight ligature is applied above the wound so as to stop the 


22 


Poisonous Arthropods 


flow of blood and lymph from that region. The wound is then 
freely excised and treated with a strong solution of permanganate 
of potash, or with lead and opium lotion. 

In recent years there have been many attempts to prepare an 
antivenom, or antiserum comparable to what has been used so 
effectively in the case of snake bites. The most promising of these 
is that of Todd (1909), produced by the immunization of suitable 
animals. This antivenom proved capable of neutralizing the venom 
when mixed in vitro and also acts both prophylaeticallv and cura- 
tively in animals. Employed eurativelv in man, it appears to have 
a very marked effect on the intense pain following the sting, and 
the evidence so far indicates that its prompt use greatly reduces 
the chance of fatal results. 

THE SOLPUGIDA, OR SOLPUGLDS 

The Solpugida are peculiar spider-like forms which are distin¬ 
guished from nearh r all other 
arachnids by the fact that 
they possess no true cephalo- 
thorax, the last two leg-bear¬ 
ing segments being distinct, 
resembling those of the abdo¬ 
men in this respect. The 
first pair of legs is not used 
in locomotion but seemingly 
functions as a second pair of 
pedipalpi. Figure 12 illus¬ 
trates the striking peculiari¬ 
ties of the group. They are 
primarily desert forms and 
occur in the warm zones of 
all countries. Of the two 
hundred or more species, 
Comstock lists twelve as 
occurring in our fauna. 
These occur primarily in the 
southwest. 

The Solpugida have long 
borne a bad reputation and regarding virulence, have been classed 
with the scorpions. Among fthe effects of their bites have been 



12 . A solpugid (Eremobates cinerea). After Com¬ 
stock. 


Mites and Ticks 


23 


described painful swelling, gangrene, loss of speech, cramps, deliri¬ 
um, unconsciousness and even death. Opposed to the numerous loose 
accounts of poisoning, there are a number of careful records by 
physicians and zoologists which indicate clearly that the effects are 
local and though they may be severe, they show not the slightest 
symptom of direct poisoning. 

More important in the consideration of the question is the fact 
that there are neither poison glands nor pores in the fangs for the 
exit of any poisonous secretion. This is the testimony of a number 
of prominent zoologists, among whom is Dr. A. Walter, who wrote 
to Robert at length on the subject and whose conclusions are pre¬ 
sented by him. 

However, it should be noted that the fangs are very powerful 
and are used in such a manner that they may inflict especially severe 
wounds. Thus, there may be more opportunity for secondary 
infection than is usual in the case of insect wounds. 

The treatment of the bite of the Solpugida is, therefore, a matter 
of preventing infection. The wound should be allowed to bleed 
freely and then washed out with a 113000 solution of corrosive 
sublimate, and, if severe, a wet dressing of this should be applied. 
If infection takes place, it should be treated in the usual man¬ 
ner, regardless of its origin. 

THE ACARINA, OR MITES AND TICKS 

A number of the parasitic Acarina evidently secrete a 
specific poison, presumably carried by the saliva, but in most cases 
its effect on man is insignificant. There is an abundant literature 
dealing with the poisonous effect of the bite of these forms, especially 
the ticks, but until recently it has been confused by failure to recog¬ 
nize that various species may transmit diseases of man, rather than 
produce injur}' through direct poisoning. We shall therefore 
discuss the Acarina more especially in subsequent chapters, dealing 
with parasitism and with disease transmission. 

Nevertheless, after the evidence is sifted, there can be no doubt 
that the bites of certain ticks may occasionally be followed by a 
direct poisoning, which may be either local or general in its effects. 
Nuttall (1908) was unable to determine the cause of the toxic effect, 
for, in Argas persicus, the species most often implicated, he failed to 
get the slightest local or general effect on experimental animals, from 
the injection of an emulsion prepared by crushing three of the ticks. 


24 


Poisonous Arthropods 


It seems clearly established that the bite of certain ticks may 
cause a temporary paralysis, or even complete paralysis, involving 
the organs of respiration or the heart, and causing death. In 1912, 
Dr. I. U. Temple, of Pendleton, Oregon, reported several cases of 
what he called “acute ascending paralysis” associated with the occur¬ 
rence of ticks on the head or the back of the neck. A typical severe 
case was that of a six year old child, who had retired in her usual 
normal health. The following morning upon arising she was unable 
to stand on her feet. She exhibited paralysis extending to the knees, 
slight temperature, no pain, sensory nerves normal, motor nerves 
completely paralyzed, reflexes absent. The following day the paral¬ 
ysis had extended to the upper limbs, and before night of the third 
day the nerves of the throat (hypoglossal) were affected. The thorax 
and larynx were involved, breathing was labored, she was unable 
to swallow liquids, phonation was impossible and she could only make 
low, gutteral sounds. At this stage, two ticks, fully distended with 
blood, Were found over the junction of the spinal column with the 
occipital bones in the hollow depression. They were removed by 
the application of undiluted creoline. Though the child’s life was 
despaired of, by the following morning she was very much improved. 
By evening she was able to speak. The paralysis gradually receded, 
remaining longest in the feet, and at the end of one week the patient 
was able to go home. 

There was some doubt as to the exact species of tick implicated 
in the cases which Dr. Temple reported, although the evidence 
pointed strongly to Dermacentor venustus.* Somewhat later, Hadwen 
(1913) reported that “tick paralysis” occurs in British Columbia, 
where it affects not only man, but sheep and probably other animals. 
It is caused by the bites of Dermacentor venustus and was experi¬ 
mentally produced in lambs and a dog (Hadwen and Nuttall, 1913). 
It is only when the tick begins to engorge or feed rapidly, some days 
after it has become attached, that its saliva produces pathogenic 
effects. 

Ulceration following tick bite is not uncommon. In many of the 
instances it is due to the file-like hypostome, with its recurved teeth, 
being left in the wound when the tick is forcibly pulled off. 

*According to Stiles, the species occurring in the Northwest which is commonly 
identified as D. venustus should be called D. andersonii (see footnote, chapter 12). 


Centipedes and Millipedes 


25 


.Se-o 








THE MYRIAPODA, OR CENTIPEDES AND MILLIPEDES 

The old class, Myriapoda includes the Diplopoda, or 
millipedes, and the Chilopoda, or centipedes. The pres¬ 
ent tendency is to raise these groups to the rank of 
classes. 

The Diplopoda 

The Diplopoda, or millipedes (fig. 13), are character¬ 
ized by the presence of two pairs of legs to a segment. 
The largest of our local myriapods belong to this group. 
They live in moist places, feeding primarily on decay¬ 
ing vegetable matter, though a few species occasion¬ 
ally attack growing plants. 

The millipedes are inoffensive and harmless. Julus 
terrestris, and related species, when irritated pour out 
over the entire body a yellowish secretion which escapes 
from cutaneous glands. It is 
volatile, with a pungent odor, 
and Phisalix (1900) has shown 
that it is an active poison when 
Mter Comstock injected into the blood of experi¬ 
mental animals. This, how¬ 
ever, does not entitle 
them to be considered 
as poisonous arthro¬ 
pods, in the sense of this 
chapter, any more than 
the toad can be con¬ 
sidered poisonous to 
man because it secretes 
a venom from its cuta¬ 
neous glands. 

The Chilopoda 

The Chilopoda, or 

centipedes (fig. 14), un¬ 
like the millipedes, are 
predaceous forms, and 
possess well developed 
poison glands for kill¬ 
ing their prey. These 




14. Two common centipedes. 

(a) Lithobius forficatus. (6) Scutigera forceps. Natural 


After Comstock. 


size; after Howard. 


26 


Poisonous Arthropods 



15. Mandible of 
Scolopendra 
cingulata 
showing 
venom 
gland. After 
Dubosq. 


glands are at the base of the first pair of legs (fig. 15), which are 
bent forward so as to be used in holding their prey. The legs 
terminate in a powerful claw, at the tip of which is the 
outlet of the poison glands. 

The poison is a limpid, homogeneous, slightly acid 
fluid, which precipitates in distilled water. Briot (1904) 
extracted it from the glands of Scolopendra morsitans , a 
species common in central France, and found that it was 
actively venomous for the ordinary experimental ani¬ 
mals. A rabbit of two kilograms weight received an 
injection of three cubic centimeters in the vein of the ear 
and died in a minute. A white rat, weighing forty-eight 
grams, received one and a half cubic centimeters in the 
hind leg. There was an almost immediate paralysis of 
the leg and marked necrosis of the tissues. 

As for the effect on man, there is little foundation for the fear 
with which centipedes are regarded. Our native species produce, 
at most, local symptoms,—sometimes severe local pain and swell¬ 
ing,-—but there is no authentic record of fatal results. In the tropics, 
some of the species attain a large size, Scolopendra gigantea reaching 
a length of nearly a foot. These forms are justly feared, and there 
is good evidence that death sometimes, though rarely, results from 
their bite. 

One of the most careful accounts of death from the sting of the 
scorpion is that of Linnell, (1914), which relates to a comparatively 
small Malayan species, unfortunately undetermined. The patient, 
a coolie, aged twenty, was admitted to a hospital after having been 
stung two days previously on the left heel. For cure, the other 
coolies had made him eat the head of the scorpion. On admission, 
the patient complained of “things creeping all over the body”. 
Temp. 102.8°. On the fourth day he had paralysis of the legs, and 
on the fifth day motor paralysis to the umbilicus, sensation being 
unaltered. On the sixth day there was retention of the urine and 
on the ninth day (first test after third day) sugar was present. On 
the thirteenth day the patient became comatose, but could be 
roused to eat and drink. The temperature on the following day fell 
below 95° and the patient was still comatose. Death fifteenth day. 

Examination of the spinal (lumbar) cord showed acute dissemi¬ 
nated myelitis. In one part there was an acute destruction of the 
anterior horn and an infiltration of round cells. In another portion 


Hexapoda, or True Insects 


27 


Clarke’s column had been destroyed. The perivascular sheaths 
were crowded with small round cells and the meninges were con¬ 
gested. Some of the cells of the anterior horn were swollen and the 
nuclei eccentric; chromatolysis had occurred in many of them. 

As for treatment, Castellani and Chalmers (1910), recommend 
bathing the part well with a solution of ammonia (one in five, or one 
in ten). After bathing, apply a dressing of the same alkali or, if 
there is much swelling and redness, an ice-bag. If necessary, hypo¬ 
dermic injections of morphine may be given to relieve the pain. 
At a later period fomentations may be required to reduce the local 
inflammation. 


THE HEXAPODA OR TRUE INSECTS 

There are a number of Hexapoda, or true insects, which are, in 
one way or another, poisonous to man. These belong primarily 
to the orders Hemiptera, or true bugs; Lepidoptera, or butterflies 
and moths (larval forms); Diptera, or flies; Coleoptera, or beetles; 
and Hymenoptera, or ants, bees, and wasps. There are various ways 
in which they may be poisonous. 

1. Piercing or biting forms may inject an irritating or poisonous 
saliva into the wound caused by their mouth-parts. 

2. Stinging forms may inject a poison, from glands at the caudal 
end of the abdomen, into wounds produced by a specially modified 
ovipositer, the sting. 

3. Nettling properties may be possessed by the hairs of the insect. 

4. Vescicating, or poisonous blood plasma , or body fluids are 
known to exist in a large number of species and may, under excep¬ 
tional circumstances, affect man. 

For convenience of discussion, we shall consider poisonous insects 
under these various headings. In this, as in the preceding discussion, 
no attempt will be made to give an exhaustive list of the poisonous 
forms. Typical instances will be selected and these will be chosen 
largely from North American species. 

PIERCING OR BITING INSECTS POISONOUS TO MAN 
Hemiptera 

Several families of the true bugs include forms which, while 
normally inoffensive, are capable of inflicting painful wounds on man. 
In these, as in all of the Hemiptera, the mouth-parts are modified 


28 


Poisonous Arthropods 



to form an organ for piercing and 
sucking. This is well shown by the 
accompanying illustration (fig. 16). 

Theupper lip, or labrum, ismuch 
reduced and immovable, the lower 
lip, or labium, is elongated to form 
a jointed sheath, within which the 
lance-like mandibles and maxillae 
are enclosed. The mandibles are 
more or less deeply serrate, depend¬ 
ing on the species concerned. 

The poison is elaborated by the salivary glands, excepting, possi¬ 
bly, in Belostoma where Locy is inclined to believe that it is secreted 
by the maxillary glands. The salivary glands 
of the Hemiptera have been the subject of 
much study but the most recent, eomprehen- 
sivepvork has been done by Bugnion and Popoff, 

(1908 and 1910) to whose text the reader is 
referred for details. 

The Hemiptera have two 
pairs of salivary glands: the 
primary gland, of which the 
efferent duct leads to the 
salivary syringe, and the 
accessory gland, of which the 
very long and flexuous duct 
empties into the primary duct 
at its point of insertion. 

Thus, when one observes the 
isolated primary gland it appears as though it 
had efferent ducts inserted at the same point. In 
Nepa and the Fulgoridce there are two accessory 
glands and therefore apparently three ducts 
at the same point on the primary gland. The 
ensemble differs greatly in appearance in different 
species but we shall show here Bugnion and 
Popoff’s figure of the apparatus of Notonecta 
maculata, a species capable of inflicting a painful 




17. 


Salivary glands of 
Notonecta maculata. 
After Bugnion and 
Popoff. 


18. Pharyngeal syrinve or 
salivary pump of Ful- 


l“";a*Pop T’ bite on man (fig. i 7 ). 














Hemiptem, or True Bugs 


29 


Accessory to the salivary apparatus there is on the ventral side 
of the head, underneath the pharynx, a peculiar organ which the 



/ 

19. Heteroptera, (a) Melanolestes picipes; (6) Notonecta undulata; (c.d) Aradus robustus 
(c) adult, (d) nymph, much enlarged; (e) Arilus cristatus; (/) Belostoma americana; 
J(g) Nabis (Coriscus) subcoleoptratus, enlarged; ( h ) Cimex lectularius. (») Oeciacus 
vicarius, much enlarged; (/) Lyctocoris fitchii, much enlarged After Lugger. 


Germans have called the “ Wanzenspritze,” or syringe. The ac¬ 
companying figure of the structure in Fulgora maculata (fig. 18) shows 
its relation to the ducts of the salivary glands and to the beak. It is 







3 ° 


Poisonous Arthropods 


made up of a dilatation forming the body of the pump, in which there 
is a chitinous piston. Attached to the piston is a strong retractor 
muscle. The function of the salivary pump is to suck up the saliva 
from the salivary ducts and to force it out through the beak. 

Of the Hemiptera reported as attacking man, we shall consider 
briefly the forms most frequently noted. 

The Notonectidae, or back swimmers, (fig. igb) are small, aquatic 
bugs that differ from all others in that they always swim on their 
backs. They are predaceous, feeding on insects and other small 
forms. When handled carelessly they are able to inflict a painful 
bite, which is sometimes as severe as the sting of a bee. In fact, 
they are known in Germany as “ Wasserbienen.” 

The Belostomatidee, or giant water bugs, (fig. 19/) include the largest 
living Hemiptera. They are attracted to lights and on account of the 
large numbers which swarm about the electric street lamps in some 
localities they have received the popular name “electric light bugs.’’ 
Our largest representatives in the northern United States belong to 
the two genera Belostoma and Banacus, distinguished from each 
other by the fact that Belostoma has a groove on the under side of 
the femur of the front leg, for the reception of the tibia. 

The salivary glands of Belostoma were figured by Leidy (1847) 
and later were studied in more detail by Locy (1884). There are 
two pairs of the glands, those of one pair being long and extending 
back as far as the beginning of the abdomen, while the others are 
about one-fourth as long. They lie on either side of the oesophagus. 
On each side of the oesophagus there is a slender tube with a 
sigmoid swelling which may serve as a poison reservoir. In addi¬ 
tion to this salivary system, there is a pair of very prominent glands 
on the ventral side of the head, opening just above the base of the 
beak. These Locy has called the “cephalic glands” and he suggests 
that they are the source of the poison. They are the homologues 
of the maxillary glands described for other Hemiptera, and it is by 
no means clear that they are concerned with the production of 
venom. It seems more probable that in Belostoma, as in other 
Hemiptera, it is produced by the salivary glands, though the question 
is an open one. 

The Belostomatidae feed not only on insects, but on small frogs, 
fish, salamanders and the like. Mathcson (1907) has recorded the 
killing of a good-sized bird by Belostoma americana. A woodpecker, 


Hemiptera , or True Bugs 


3 1 



Reduvius (Opsiccetus) 
personatus. (x2). 


cause 

shooting pains that 
may extend through¬ 
out the arm and that 
they may be felt for several days. 

Relief from the pain may be obtained by 
the use of dilute ammonia, or a menthol 
ointment. In the not uncommon case of 
secondary infection the usual treatment for 
that should be adopted. 

The Reduviidas, or assassin-bugs are cap¬ 
able of inflicting very painful wounds, as 

most collect¬ 


or flicker, was heard to utter cries of distress, 
and fluttered and fell from a tree. On exam¬ 
ination it was found that a bug of this species 
had inserted its beak into the back part of 
the skull and was apparently busily engaged 
in sucking the blood or brains of the bird. 
Various species of Belostoma have been cited 
as causing painful bites in man. We can 
testify from personal experience that the bite 
of Belostoma americana may almost immedi¬ 
ately cause severe, 




21. 


(a) Reduvius personatus, 
nymph. 

Photograph by M. V. S. 


(b) Reduvius personatus, adult (x2) 
Photograph by M. V. S. 


ors of Hemip¬ 
tera know to 
their sorrow. 

Some species are frequently to be 
found in houses and outhouses and 
Dr. Howard suggests that many of 
the stories of painful spider bites 
relate to the attack of these forms. 

An interesting psychological study 
was afforded in the summer of 1899, 
by the “kissing-bug” scare which 
swept over the country. It was 
reported in the daily papers that a 
new and deadly bug had made its 
appearance, which had the unpleasant 
habit of choosing the lips or cheeks 









32 


Poisonous Arthropods 


for its point of attack on man. So widespread were the stories 
regarding this supposedly new insect that station entomologists all 

over the country began to receive sus¬ 
pected specimens for identification. At 
Cornell there were received, among 
others, specimens of stone-flies, may¬ 
flies and even small moths, with in¬ 
quiries as to whether they were “kiss- 
ing-bugs.” 

Dr. L. 0 . Howard has shown that the 
scare had its origin in newspaper reports 
of some instances of bites by either 
Melanolestes picipes (fig. 19a) or Opsi- 
coetes personatus (fig. 20), in the vicinity 
of Washington, D. C. He then discusses 
in considerable detail the more promi- 
22 ' 1 Howa U rd blguttatus ’ (x2) ' Aftcr nen ^ the Reduviidse which, with 

greater or less frequency pierce the skin 
of human beings. These are Opsicoetes personatus, Melanolestes 
picipes, Coriscus suhcoleoptratus (fig. i9g), Rasahus tlioracicus. 
Rasahus biguttatus (fig. 22), Conorhinus sanguisugus (fig. 71), and C. 
abdominalis (fig. 23). 

One of the most interesting of these species is Reduvius personatus, 
(= Opsiccetus personatus) , which is popularly known as the ‘ ‘ masked 
bed-bug hunter.” It owes this 
name to the fact that the imma¬ 
ture nymphs (fig. 21) have their 
bodies and legs completely covered 
by dust and lint, and that they 
are supposed to prey upon bed¬ 
bugs. LeConte is quoted by How¬ 
ard as stating that * * This species is 
remarkable for the intense pain 
caused by its bite. I do not know 
whether it ever willingly plunges 
its rostrum into any person, but 
when caught, or unskilfully handled 
it always stings. In this case the 
pain is almost equal to the bite of a snake, and the swelling and 
irritation which result from it will sometimes last for a week.” 











Diptera 


33 


A species which very commonly attacks man is Conorhinus 
sanguisugus , the so-called “big bed-bug” of the south and southern 
United States. It is frequently found in houses and is known to 
inflict an exceedingly painful bite. As in the case of a number of 
other predaceous Hemiptera, the salivary glands of these forms are 
highly developed. The effect of the bite on their prey and, as Marlatt 
has pointed out, the constant and uniform character of the symptoms 
in nearly all cases of bites in man, clearly indicate that their saliva 
contains a specific substance. No satisfactory studies of the secre¬ 
tions have been made. On the other hand, Dr. Howard is doubt¬ 
less right in maintaining that the very serious results which some¬ 
times follow the bite are due to the introduction of extraneous poison 
germs. This is borne out by the symptoms of most of the cases 
cited in literature and also by the fact that treatment with corrosive 
sublimate, locally applied to the wound, has yielded favorable results. 

Other Hemiptera Reported as Poisonous to Man —A large number 
of other Hemiptera have been reported as attacking man. Of these, 
there are several species of Lygaeidas, Coreidae, and Capsidas. Of the 
latter, Lygns pratensis, the tarnished plant-bug, is reported by 
Professor Crosby as sucking blood. Orthotylus flavosparsus is another 
Capsid which has been implicated. Empoasca malt and Platymetopius 
acutus of the Jassidas have also been reported as having similar 
habits. 

Whenever the periodical cicada or “seventeen-year locust” be¬ 
comes abundant, the newspapers contain accounts of serious results 
from its bites. The senior author has made scores of attempts to 
induce this species to bite and only once successfully. At that 
time the bite was in no wise more severe than a pin-prick. A stu¬ 
dent in our department reports a similar experience. There is no 
case on record which bears evidence of being worthy of any credence, 
whatsoever. 

Under the heading of poisonous Hemiptera we might consider the 
bed-bugs and the lice. These will be discussed later, as parasites 
and as carriers of disease, and therefore need only be mentioned here. 

DIPTERA 

Several species of blood-sucking Diptera undoubtedly secrete a 
saliva possessing poisonous properties. Chief among these are the 
Culicidae, or mosquitoes, and the Simuliidas, or black-flies. As we 
shall consider these forms in detail under the heading of parasitic 


34 


Poisonous Arthropods 


species and insects transmitting disease, we shall discuss here only 
the poison of the mosquitoes. 

It is well known that mosquitoes, when they bite, inject into the 
wound a minute quantity of poison. The effect of this varies accord¬ 
ing to the species of mosquito and also depends very much on the 
susceptibility of the individual. Soon after the bite a sensation of 
itching is noticed and often a wheal, or eminence, is produced on the 
skin, which may increase to a considerable swelling. The scratching 
which is induced may cause a secondary infection and thus lead to 
serious results. Some people seem to acquire an immunity against 
the poison. 

The purpose of this irritating fluid may be, as Reaumur suggested, 
to prevent the coagulation of the blood and thus not only to cause 
it to flow freely when the insect bites but to prevent its rapid coagula¬ 
tion in the stomach. Obviously, it is not developed as a protective 
fluid, and its presence subjects the group to the additional handicap 
of the vengeance of man. 

As to the origin of the poison, there has been little question, 
until recent years, that it was a secretion from the salivary glands. 


Macloskie (1888) showed 
that each gland is sub¬ 
divided into three lobes, 
the middle of which differs 
from the others in having 
evenly granulated contents 
and staining more deeply 



24. Diagram of a longitudinal section of a mosquito. 


than the others (fig. 24). This middle lobe he regarded as the source 
of the poison. Brack, (1911), by the use of water, glycerine, chloro¬ 
form, and other fluids, extracted from the bodies of a large number 
of mosquitoes a toxine which he calls culicin. This he assumes 
comes from the salivary glands. Animal experimentation showed 
that this extract possessed hemolytic powers. Inoculated into the 
experimenter’s own skin it produced lesions which behaved exactly 
as do those of mosquito bites. 

Similarly, most writers on the subject have concurred with the 
view that the salivary glands are the source of the poison. How¬ 
ever, recent work, especially that of Nuttall and Shipley (1903), 
and Schaudinn (1904), has shown that the evidence is by no means 
conclusive. Nuttall dissected out six sets (thirty-six acini) of glands 
from freshly killed Culex pipiens and placed them in a drop of salt 



Diptera 


35 


solution. The drop was allowed to dry, it being thought that the 
salt crystals would facilitate the grinding up of the glands with the 
end of a small glass rod, this being done under microscopic control. 
After grinding up, a small drop of water was added of the size of the 
original drop of saline, and an equal volume of human blood taken 
from the clean finger-tip was quickly mixed therewith, and the whole 
drawn up into a capillary tube. Clotting was not prevented and no 
hemolysis occurred. Salivary gland emulsion added to a dilute 
suspension of corpuscles did not lead to hemolysis. This experi¬ 
ment was repeated a number of times, with slight modification, but 
with similar results. The data obtained from the series “do not 
support the hypothesis that the salivary glands, at any rate in Culex 
pipiens, contain a substance which prevents coagulation.” 

Much more detailed, and the more important experiments made 
along this line, are those of Schaudinn (1904). The results of these 
experiments w^ere published in connection with a technical paper 
on the alternation of generations and of hosts in Trypanosoma and 
Spirochoeta, and for this reason seem to have largely escaped the notice 
of entomologists. They are so suggestive that w r e shall refer to them 
in some detail. 

Schaudinn observed that the three oesophageal diverticula (com¬ 
monly, but incorrectly, knowm as the “sucking stomach”) (fig. 24) 
usually contain large bubbles of gas and in addition, he always found 
yeast cells. On the ground of numerous observations, Schaudinn 
was convinced that these yeast plants are normal and constant 
commensals of the insect. He regarded them as the cause of the gas 
bubbles to be found in diverticula. It was found that as the insect 
fed, from time to time the abdomen underwent convulsive contrac¬ 
tions which resulted in the emptying of the oesophageal diverticula and 
the salivary glands through blood pressure. 

In order to test the supposed toxic action of the salivary glands, 
Schaudinn repeatedly introduced them under his skin and that of 
his assistant, in a drop of salt solution, and never obtained a sugges¬ 
tion of the irritation following a bite of the insect, even though the 
glands were carefully rubbed to fragments after their implantation. 
Like Nuttall, he failed to get satisfactory evidence that the secre¬ 
tion of the salivary glands retarded coagulation of the blood. 

He then carefully removed the oesophageal diverticula with their 
content of yeast and introduced them into an opening in the skin 
of the hand. Within a few seconds there was noticeable the charac- 


36 


Poisonous Arthropods 


teristic itching irritation of the mosquito bite; and in a short time 
there appeared reddening and typical swelling. This was usually 
much more severe than after the usual mosquito bite, and the swell¬ 
ing persisted and itched longer. This was because by the ordinary 
bite of the mosquito most of the yeast cells are again sucked up, 
while in these experiments they remained in the wound. These 
experiments were repeated a number of times on himself, his assistant 
and others, and always with the same result. From them Schaudinn 
decided that the poisonous action of the mosquito bite is caused by 
an enzyme from a commensal fungus. These conclusions have not, 
as yet, been satisfactorily tested. 

Relief from the effect of the mosquito bite may be obtained by 
bathing the swellings with weak ammonia or, according to Howard, 
by using moist soap. The latter is to be rubbed gently on the punc¬ 
ture and is said to speedily allay the irritation. Howard also quotes 
from the Journal of Tropical Medicine and Hygiene to the effect that 
a few drops of a solution of thirty to forty grains of iodine to an ounce 
of saponated petroleum rubbed into the mosquito bite, or wasp sting, 
allay the pain instantaneously. 

Methods of mosquito control will be discussed later, in consider¬ 
ing these insects as parasites and as carriers of disease. 

STINGING INSECTS 

The stinging insects all belong to the order Hymenoptera. In a 
number of families of this group the ovipositor is modified to form a 
sting and is connected with poison-secreting glands. We shall 
consider the apparatus of the honey-bee and then make briefer refer¬ 
ence to that of other forms. 

Apis mellifica, the honey bee —The sting of the worker honey¬ 
bee is situated within a so-called sting chamber at the end of the 
abdomen. This chamber is produced by the infolding of the greatly 
reduced and modified eighth, ninth and tenth abdominal segments 
into the seventh.* From it the dart-like sting can be quickly ex- 
serted. 

The sting (fig. 25) is made up of a central shaft, ventro-laterad of 
which are the paired lancets, or darts, which are provided with sharp, 
recurved teeth. Still further laterad lie the paired whitish, finger- 

*It should be remembered that in all the higher Hymenoptera the first ab¬ 
dominal segment is fused with the thorax and that what is apparently the sixth 
segment is, in reality, the seventh. 



Stinging Insects 


37 


like sting palpi. Comparative morphological as well as embryologi- 
cal studies have clearly established that these three parts corres¬ 
pond to the three pairs of 
gonopophyses of the ovipositor 
of more generalized insects. 

An examination of the inter¬ 
nal structures (fig. 26) reveals 
two distinct types of poison 
glands, the acid-secreting and 
the alkaline-secreting glands, 

25. Sting of a honey bee. Psn Sc, base of acid 
and a prominent poison reser- poison gland; B Cl. alkaline poison gland; 

. T , I*.* ,1 • Stn Pip, sting palpi; Sh B, bulb of sting; 

VOir. in addition, there IS a Sh a, basal arm; Let, lancets or darts; Sh s, 

,, . . shaft of sting. Modified from Snodgrass. 

small pair of accessory struct¬ 
ures which have been called lubricating glands, on account of the 
supposed function of their product. The acid-secreting gland empties 
into the distal end of the poison reservoir which in turn pours the 
secretion into the muscular bulb-like enlargement at the base of the 
shaft. The alkaline secreting gland empties into the bulb ventrad 
of the narrow neck of the reservoir. 

The poison is usually referred to as formic acid. That it is not so 
easily explained has been repeatedly shown and is evidenced by the 
presence of the two types of glands. Carlet maintains that the pro¬ 
duct of either gland is in itself innocent, 
—it is only when they are combined that 
the toxic properties appear. 

The most detailed study of the poison 
of the honey-bee is that of Josef Langer 
(1897), who in the course of his work used 
some 25,000 bees. Various methods of 
obtaining the active poison for experi¬ 
mental purposes were used. For obtaining 
the pure secretion, bees were held in the 
fingers and compressed until the sting was 
exserted, when a clear drop of the poison 
was visible at its tip. This was then taken 
up in a capillary tube or dilute solutions 
bee. Modified from Snod- obtained by dipping the tip of the sting into 
a definite amount of distilled water. 

An aqueous solution of the poison was more readily obtained by 
pulling out the sting and poison sacs by means of forceps, and grinding 









38 


Poisonous Arthropods 


them up in water. The somewhat clouded fluid was then filtered 
one or more times. For obtaining still greater quantities, advantage 
was taken of the fact that while alcohol coagulates the poison, the 
active principle remains soluble in water. Hence the stings with 
the annexed glands where collected in 96 per cent alcohol, after 
filtering off of the alcohol were dried at 40° C., then rubbed to a fine 
powder and this was repeatedly extracted with water. Through 
filtering of this aqueous extract there was obtained a yellowish- 
brown fluid which produced the typical reactions, according to con¬ 
centration of the poison. 

The freshly expelled drop of poison is limpid, of distinct acid 
reaction, tastes bitter and has a delicate aromatic odor. On evapora¬ 
tion, it leaves a sticky residue, which at 100 degrees becomes fissured, 
and suggests dried gum arabic. The poison is readily soluble in 
water and possesses a specific gravity of 1.1313. On drying at room 
temperature, it leaves a residue of 30 per cent, which has not lost in 
poisonous action or in solubility. In spite of extended experiments, 
Langer was unable to determine the nature of the active principle. 
He showed that it was not, as had been supposed, an albuminous 
body, but rather an organic base. 

The pure poison, or the two per cent aqueous solution, placed on 
the uninjured skin showed absolutely no irritating effect, though it 
produced a marked reaction on the mucus membrane of the nose or 
eye. A single drop of one-tenth per cent aqueous solution of the 
poison brought about a typical irritation in the conjunctiva of the 
rabbit’s eye. On the other hand, the application of a drop of the 
poison, or its solution, to the slightest break in the skin, or by means 
of a needle piercing the skin, produced typical effects. There is pro¬ 
duced a local necrosis, in the neighborhood of which there is infiltra¬ 
tion of lymphocytes, oedema, and hyperaemia. 

The effect of the sting on man (fig. 27) is usually transitory but 
there are some individuals who are made sick for hours, by a single 
sting. Much depends, too, on the place struck. It is a common 
experience that an angry bee will attempt to reach the eye of its 
victim and a sting on the lid may result in severe and prolonged 
swelling. In the case of a man stung on the cheek, Legiehn observed 
complete aphonia and a breaking out of red blotches all over the 
body. A sting on the tongue has been known to cause such collateral 
oedema as to endanger life through suffocation. Cases of death of 
man from the attacks of bees are rare but are not unknown. Such 


Stinging Insects 


39 


results are usually from a number of stings but, rarely, death has 
been known to follow a single sting, entering a blood vessel of a 
particularly susceptible individual. 

It is clearly established that partial immunity from the effects 
of the poison may be acquired. By repeated injections of the venom, 
mice have been rendered capable of bearing doses that certainly 
would have killed them at first. It is a well-knowm fact that most 
bee-keepers become gradually hardened to the stings, so that the 
irritation and the swelling become less and less. Some individuals 




Effect of bee stings. After Root. 


have found this immunity a temporary one, to be reacquired each 
season. A striking case of acquired immunity is related by the 
Roots in their “ABC and X Y Z of Bee Culture.” The evidence 
in the case is so clear that it should be made more widely available 
and hence we quote it here. 

A young man who was determined to become a bee-keeper, was so 
susceptible to the poison that he was most seriously affected by a 
single sting, his body breaking out with red blotches, breathing grow¬ 
ing difficult, and his heart action being painfully accelerated. “We 
finally suggested taking a live bee and pressing it on the back of his 
hand until it merely pierced his skin with the sting, then immediately 
brushing off both bee and sting. This was done and since no serious 
effect followed, it was repeated inside of four or five days. This 
was continued for some three or four weeks, when the patient began to 
have a sort of itching sensation all over his body. The hypodermic 



40 


Poisonous Arthropods 


injections of bee-sting poison were then discontinued. At the end 
of a month they were repeated at intervals of four or five days. 
Again, after two or three weeks the itching sensation came on, but 
it was less pronounced. The patient was given a rest of about a 
month, when the doses were repeated as before.” By this course 
of treatment the young man became so thoroughly immunized that 
neither unpleasant results nor swelling followed the attacks of the 
insects and he is able to handle bees with the same freedom that any 
experienced bee-keeper does. 

In an interesting article in the Entomological News for November, 
1914, J. H. Lovell calls attention to the fact that “There has been a 
widespread belief among apiarists that a beekeeper will receive more 
stings when dressed in black than when wearing white clothing. 
A large amount of evidence has been published in the various bee 
journals showing beyond question that honey-bees under certain 
conditions discriminate against black. A few instances may be 
cited in illustration. Of a flock of twelve chickens running in a bee- 
yard seven black ones were stung to death, while five light colored 
ones escaped uninjured. A white dog ran among the bee-hives 
without attracting much attention, while at the same time a black 
dog was furiously assailed by the bees. Mr. J. D. Byer, a prominent 
Canadian beekeeper, relates that a black and white cow, tethered 
about forty feet from an apiary, was one afternoon attacked and 
badly stung by bees. On examination it was found that the black 
spots had five or six stings to one on the white. All noticed this fact, 
although no one was able to offer any explanation. A white horse 
is in much less danger of being stung, when driven near an apiary, 
than a black one. It has, indeed, been observed repeatedly that 
domestic animals of all kinds, if wholly or partially black, are much 
more liable to be attacked by bees, if they wander among the hives, 
than those which are entirely white. 

In order to test the matter experimentally, the following series 
of experiments was performed. In the language of the investi¬ 
gator : 

“On a clear, warm day in August I dressed wholly in white with 
the exception of a black veil. Midway on the sleeve of my right arm 
there was sewed a band of black cloth ten inches unde. I then 
entered the bee-yard and, removing the cover from one of the hives, 
lifted a piece of comb with both hands and gently shook it. Instantly 
many of the bees flew to the black band, which they continued to 


Stinging Insects 


4i 


attack as long as they were disturbed. Not a single bee attempted 
to sting the left sleeve, which was of course entirely white, and. very 
few even alighted upon it.” 

‘‘This experiment was repeated a second, third and fourth time; 
in each instance with similar results. I estimated the number of bees 
on the band of black cloth at various moments was from thirty to 
forty; it was evident from their behavior that they were extremely 
irritable. To the left white sleeve and other portions of my clothing 
they paid very little attention; but the black veil was very frequently 
attacked.” 

‘‘A few days later the experiments were repeated, but the band of 
black cloth, ten inches wide, was sewed around my left arm instead 
of around the right arm as before. When the bees were disturbed, 
after the hive cover had been removed, they fiercely attacked the 
band of black cloth as in the previous experiences; but the right white 
sleeve and the white suit were scarcely noticed. At one time a part 
of the black cloth was almost literally covered with furiously stinging 
bees, and the black veil was assailed by hundreds. The bees behaved 
in a similar manner when a second hive on the opposite side of the 
apiary was opened.” 

‘ ‘A white veil which had been procured for this purpose, was next 
substituted for the black veil. The result was most surprising, 
for, whereas in the previous experiments hundreds of bees had 
attacked the black veil, so few flew against the white veil as to cause 
me no inconvenience. Undoubtedly beekeepers will find it greatly 
to their advantage to wear white clothing when working among their 
colonies of bees and manipulating the frames of the hives.” 

When a honey-bee stings, the tip of the abdomen, with the entire 
sting apparatus, is torn off and remains in the wound. Here the 
muscles continue to contract, for some minutes, forcing the barbs 
deeper and deeper into the skin, and forcing out additional poison 
from the reservoir. 

Treatment, therefore, first consists in removing the sting without 
squeezing out additional poison. This is accomplished by lifting 
and scraping it out with a knife-blade or the fingernail instead of 
grasping and pulling it out. Local application of alkalines, such as 
weak ammonia, are often recommended on the assumption that the 
poison is an acid to be neutralized on this manner, but these are of 
little or no avail. They should certainly not be rubbed in, as that 
would only accelerate the absorption of the poison. The use of 


42 


Poisonous Arthropods 


cloths wrung out in hot water and applied as hot as can be borne, 
affords much relief in the case of severe stings. The application of 
wet clay, or of the end of a freshly cut potato is sometimes helpful. 

In extreme cases, where there is great susceptibility, or where 
there may have been many stings, a physician should be called. He 
may find strychnine injections or other treatment necessary, if 
general symptoms develop. 


Other Stinging Forms—Of the five thousand, or more, species 
of bees, most possess a sting and poison apparatus and some of the 
larger forms are capable of inflicting a much more painful sting than 



that of the common honey-bee. In fact, some, like the bumble bees, 
possess the advantage that they do not lose the sting from once using 
it, but are capable of driving it in repeatedly. In the tropics there 
are found many species of stingless bees but these arc noted for their 
united efforts to drive away intruders by biting. Certain species 
possess a very irritating saliva which they inject into the wounds. 

The ants are not ordinarily regarded as worthy of consideration 
under the heading of “stinging insects’’ but as a matter of fact, 
most of them possess well developed stings and some of them, especi¬ 
ally in the tropics, are very justly feared. Even those which lack 
the sting possess well-developed poison glands and the parts of the 
entire stinging apparatus, in so far as it is developed in the various, 
species, may readily be homologized with those of the honey-bee. 











Stinging Insects 


43 


The ants lacking a sting are those of the subfamily Camponotinae, 
which includes the largest of our local species. It is an interesting 
fact that some of these species possess the largest poison glands and 
reservoir (fig. 28) and it is found that when they attack an enemy 
they bring the tip of the abdomen forward and spray the poison in 
such a way that it is introduced into the wound made by the powerful 
mandibles. 

More feared than any of the other Hymenoptera are the hornets 
and wasps. Of these there are many species, some of which attain 



29. A harmless, but much feared larva, the "tomato worm.” 
Natural size. Photograph by M. V. S. 


a large size and are truly formidable. Phisalix (1897), has made a 
study of the venom of the common hornet and finds that, like the 
poison of the honey-bee, it is neither an albuminoid nor an alkaloid. 
Its toxic properties are destroyed at 120° C. Phisalix also says that 
the venom is soluble in alcohol. If this be true, it differs in this 
respect from that of the bee. An interesting phase of the w r ork of 
Phisalix is that several of her experiments go to show that the venom 
of hornets acts as a vaccine against that of vipers. 

NETTLING INSECTS 

So far, we have considered insects which possess poison glands 
connected with the mouth-parts or a special sting and which actively 




44 


Poisonous Arthropods 


inject their poison into man. There remain to be considered those 
insects which possess poisonous hairs or body fluids which, under 
favorable circumstances, may act as poisons. To the first of these 
belong primarily the larvae of certain Lepidoptera. 


LEPIDOPTERA 

When we consider the reputedly poisonous larvae of moths and 
butterflies, one of the first things to impress us is that we cannot 



30. Another innocent but much maligned caterpillar, the larva of the Regal moth. 
. Photograph by M. V. S. 


judge by mere appearance. Various species of Sphingid, or hawk- 
moth larvae, bear at the end of the body a chitinous horn, which is 
often referred to as a “sting” and regarded as capable of inflicting 
dangerous wounds. It would seem unnecessary to refer to this 
absurd belief if it were not that each summer the newspapers con¬ 
tain supposed accounts of injury from the “tomato worm” (fig. 29) 
and others of this group. The grotesque, spiny larva (fig. 30) of 
one of our largest moths, Citheronia regalis is much feared though 
perfectly harmless, and similar instances could be multiplied. 

But if the larva; are often misjudged on account of their ferocious 
appearance, the reverse may be true. A group of most innocent 
looking and attractive caterpillars is that of the flannel-moth larvae, 






Nettling Insects 


45 


of which Lagoa crispata may be taken as an example. Its larva 
(fig. 31) has a very short and thick body, which is fleshy and com- 



31. The flinnel moth (Lagoa crispata). (a) Poisonous larva. 



31. ( b ) Adult. Enlarged. Photographs by M. V. S. 

pletely covered and hidden by long silken hairs of a tawny or brown 
color, giving a convex form to the upper side. Interspersed among 








46 


Poisonous Arthropods 


these long hairs are numer¬ 
ous short spines connected 
with underlying hvpoder- 
mal poison glands. These 
hairs are capable of pro¬ 
ducing a marked nettling 
effect when they come in 
contact with the skin. 
This species is found in 
our Atlantic and Southern 
States. Satisfactory 
studies of its poisonous 
hairs and their glands have 
not yet been made. 

Sihine stimulea ( Em - 
pretia stimulea), or the 
saddle-back caterpillar 
(fig. 32), is another which possesses nettling hairs. This species 
belongs to the group of Eucleidae, or slug caterpillars. It can be 
readily recognized 
by its flattened 
form, lateral, brist¬ 
ling spines and by 
the large green 
patch on the back 
resembling a 
saddle-cloth, while 
the saddle is repre¬ 
sented by an oval, 
purplish-brown 
spot. The small 
spines are veno¬ 
mous and affect 
some persons very 
painfully. The 
larva feeds on the 
leaves of a large 
variety of forest 
trees and also on 
cherry, plum, and 




; ; V’. ■ :v. ___ s _ 5 __ 

32 The poisonous saddle back caterpillar. Empretia 
(Sibine) stimulea. Photograph by M. V. S. 


33a. Io moth larvae on willow. Photograph by M.V. S. 











Nettling Insects 47 

even corn leaves. It is to be found throughout the Eastern and 
Southern United States. 

Automeris io is the best known of the nettling caterpillars. It is 
the larva of the Io moth, one of the Satumiidae. The mature eater- 



336. Io moth. Full grown larva. Photograph by M. V. S. 



33c. Io moth. Adult. Photograph by M. V. S. 


pillar, (fig. 33), which reaches a length of two and one-half inches, is 
of a beautiful pale green with sublateral stripes of cream and red color 
and a few black spines among the green ones. The green radiating 
spines give the body a mossy appearance. They are tipped with a 








48 


Poisonous Arthropods 


slender chitinous hair whose tip is readily broken off in the skin and 
whose poisonous content causes great irritation. Some individuals 
are very susceptible to the poison, while others are able to handle 
the larvae freely without any discomfort. The larvae feed on a wide 
range of food plants. They are most commonly encountered on 
coni and on willow, because of the opportunities for coming in contact 
with them. 

The larvae of the brown-tail moth (Euproctis chrysorrlioea,) (fig. 
35 and 36), where they occur in this country, are, on account of their 
great numbers, the most serious of all poisonous caterpillars. It is 



35. Larva of brown-tail moth. (Natural size). Photograph by M. V. S. 


not necessary here, to go into details regarding the introduction of 
this species from Europe into the New England States. This is all 
available in the literature from the United States Bureau of Entomol¬ 
ogy and from that of the various states which are fighting the species. 
Suffice to say, there is every prospect that the pest will continue to 
spread throughout the Eastern United States and Canada and that 
wherever it goes it will prove a direct pest to man as well as to his 
plants. 

Very soon after the introduction of the species there occurred in 
the region where it had gained a foothold, a mysterious dermatitis of 
man. The breaking out which usually occurred on the neck or other 
exposed part of the body was always accompanied by an intense 









Nettling Insects 


49 


itching. It was soon found that this dermatitis was caused by certain 
short, barbed hairs of the brown-tail caterpillars and that not only the 
caterpillars but their cocoons and even the adult female moths might 
harbor these nettling hairs and thus give rise to the irritation. In 
many cases the hairs were wafted to clothing on the line and when this 
was worn it might cause the same trouble. Still worse, it was found 
that very serious internal injury was often caused by breathing or 
swallowing the poisonous hairs. 

The earlier studies seemed to indicate that the irritation was 
purely mechanical in origin, the result of the minute barbed hairs 



36. Browntail moths. One male and two females. Photograph by 
M.V. S. 


working into the skin in large numbers. Subsequently, however, 
Dr. Tyzzer (1907) demonstrated beyond question that the trouble 
was due to a poison contained in the hairs. In the first place, it is 
only the peculiar short barbed hairs which will produce the dermatitis 
when rubbed on the skin, although most of the other hairs are sharply 
barbed. Moreover, it was found that in various ways the nettling 
properties could be destroyed without modifying the structure of the 
hairs. This was accomplished by baking for one hour at no° C, by 
warming to 6o° C in distilled water, or by soaking in one per cent, or in 
one-tenth per cent, of potassium hydrate or sodium hydrate. The 
most significant part of his work was the demonstration of the fact 



50 


Poisonous Arthropods 


V 


w 


that if the nettling hairs are mingled with blood, they immediately 
produce a change in the red corpuscles. These at once become 

coarsely crenated, and the 
roleaux are broken up in the 
vicinity of the hair (fig. 37 b). 
The corpuscles decrease in 
size, the coarse crenations 
are transformed into slender 
spines which rapidly disap¬ 
pear, leaving the corpuscles 
in the form of spheres, the 
light refraction of which con¬ 
trasts them sharply with the 
normal corpuscles. The 
reaction always begins at the 

(a) Ordinary hairs and three poison hairs of sub- . . , . , r ., , • 

dorsal and lateral tubercles of the larva of the basal Sharp pOUlt OI the hair. 
browntail moth. Drawing by Miss Kephart. R ^ ^ produced by 

purely mechanical means, such as the mingling of minute par¬ 
ticles of glass wool, the barbed hairs of a tussock moth, or the other 
coarser hairs of the brown-tail, with the blood. 

The question of the source of the poison has been studied in our 
laboratory by Miss Cornelia 


37. 



Kephart. She first confirmed 
Dr. Tyzzer’s general results 
and then studied carefully fixed 
specimens of the larvae to 
determine the distribution of 
the hairs and their relation to 
the underlying tissues. 

The poison hairs (fig. 37), 
are found on the subdorsal 
and lateral tubercles (fig. 38), 
in bunches of from three to 
twelve on the minute papillae 
with which the tubercles are 
thickly covered. The under¬ 
lying hypodermis is very 
greatly thickened, the cells 
being three or four times the length of the ordinary hypodcrmal 
cells and being closely crowded together. Instead of a pore canal 


37. 


(6) Effect of the poison on the blood cor¬ 
puscles of man. After Tyzzer. 













Nettling Insects 


5i 


through the cuticula for each individual hair, there is a single pore 
for each papillae on a tubercle, all the hairs of the papilla being 

connected with the 
underlying cells 
through the same 
pore canal, (figs. 
39 and 40). 

The hypodermis 
of this region is of 
two distinct types 
of cells. First, 
there is a group of 
slender fusiform 
cells, one for each 
poison hair on the 
papilla, which are 
the trichogen, or 
hair-formative cells. They are crowded to one side and towards 
the basement membrane by a series of much larger, and more promi¬ 
nent cells (fig. 40), of which there is a single one for each papilla. 
These larger cells have a granular protoplasm with large nuclei and 
are obviously actively secreting. They are so characteristic in 
appearance as to leave no question but that they are the true 
poison glands. 

Poisonous larvae of many other species have been reported from 
Europe and especially from the tropics but the above-mentioned 
species are the more important of those occurring in the United States 
and will serve as types. It should be noted in this connection that 



38. Cross section of the larva of the browntail moth showing the 
tubercles bearing the poison hairs. Drawing by Miss 
Kephart. 



39. Epithelium underlying poison hairs of the larva of the 
browntail moth. Drawing by Miss Kephart. 















5 2 


Poisonous Arthropods 



40. Same as figure 39, on larger scale. 


through some curious mis¬ 
understanding Goeldi (1913) 
has featured the larva of 
Orgyia leucostigma , the white- 
marked tussock moth, as the 
most important of the poi¬ 
sonous caterpillars of this 
country. Though there are 
occasional reports of irritation 
from its hairs such cases are 
rare and there is no evidence 
that there is any poison pres¬ 
ent. Indeed, subcutaneous 
implantation of the hairs 
leads to no poisoning, but merely to temporary irritation. 

Occasionally, the hairs of certain species of caterpillars find lodge¬ 
ment in the conjunctiva, cornea, or iris of the eye of man and give 
rise to the condition known as opthalmia nodosa. The essential 
feature of this trouble is a nodular conjunctivitis which simulates 
tuberculosis of the conjunctiva and hence has been called pseudo- 
tubercular. It may be distinguished microscopically by the presence 
of the hairs. 

Numerous cases of opthalmia nodosa are on record. Of those 
from this country, one of the most interesting is reported by de 
Schweinit z and 
Shumway (1904). It 
is that of a child of 
fifteen years whose 
eye had become in¬ 
flamed owing to the 
presence of some for¬ 
eign body. Down¬ 
ward and inward on 
the bulbar conjunc¬ 
tiva were a number 
of flattened, grayish- 
yellow nodules, be¬ 
tween which was a 
marked congestion of 

+ mn iiinr'-ti-u-ol 41 - Nodular conjunctivitis in the eye of a child. 

tne conjunctival and DeSchwcinitz and Shumway. 






















Nettling Insects 


53 


episcleral vessels (fig. 41a). Twenty-seven nodules could be differ¬ 
entiated, those directly in the center of the collection being some¬ 
what confluent and 
assuming a crescen¬ 
tic and circular ap¬ 
pearance. The nod¬ 
ules were excised 
and, on sectioning, 
were found to be 
composed of a layer 
of spindle cells and 
round cells, outside 
of which the tissue 
was condensed into 
a capsule. The 
interior consisted of 
epithelioid cells, be¬ 
tween which was a 
considerable inter¬ 
cellular substance. Directly in the center of a certain number of 
nodules was found the section of a hair (fig. 416). The evidence 
indicated that the injury had resulted from playing with caterpillars 
of one of the Arctiid moths, Spilosoma virginica. Other reported 
cases have been caused by the hairs of larvae of Lasiocampa rubi, 
L. pini, Porthetria dispar, Psilura monacha and Cnethocampa 
processionea. 

Relief from Poisoning by Nettling Larvae—The irritation from 
nettling larvae is often severe and, especially in regions where the 
brown-tail abounds, inquiries as to treatment arise. In general, it 
may be said that cooling lotions afford relief, and that scratching, 
with the possibilities of secondary infection, should be avoided, in 
so far as possible. 

Among the remedies usually at hand, weak solutions of ammonia, 
or a paste of ordinary baking soda are helpful. Castellani and Chalm¬ 
ers recommend cleaning away the hairs by bathing the region with 
an alkaline lotion, such as two per cent solution of bicarbonate of 
soda, and then applying an ointment of ichthyol (10%). 






54 


Poisonous Arthropods 


In the brown-tail district, there are many proprietary remedies of 
which the best ones are essentially the following, as recommended 
by Kirkland (1907): 

Carbolic acid. drachm. 

Zinc oxide. }4 oz. 

Lime water. 8 oz. 

Shake thoroughly and nib well into the affected parts. 

In some cases, and especially where there is danger of secondary 
infection, the use of a weak solution of creoline (one teaspoonful to a 
quart of water), is to be advised. 


Vescicating Insects and those Possessing Other Poisons in 
their Blood Plasma 


We have seen that certain forms, for example, the 
poisonous spiders, not only secrete a toxine in their 
poison glands, but that such a substance may be ex¬ 
tracted from other parts of their body, or even their 
eggs. There are many insects which likewise possess a 
42a. Blister bee- poisonous blood plasma. Such forms have been well 

tie. 

designated by Taschenberg as cryptotoxic (xpuxTO<; = 
hidden). We shall consider a few representative forms. 



The Blister Beetles —Fore¬ 
most among the cryptotoxic 
insects are the Meloidce or 
“blister beetles,” to which the 
well-known “Spanish fly” (fig. 
42a), formerly very generally 
used in medical practice, be¬ 
longs. The vescicating property 
is due to the presence in the 
blood plasma of a peculiar, 
volatile, crystalline substance 
known as cantharidin, which is 
especially abundant in the repro¬ 
ductive organs of the beetle. Ac¬ 
cording to Robert, the amount 
of this varies in different species 
from .4 or .5% to 2.57% of the 
dry weight of the beetle. 



426. An American blister beetle. Meloe an- 
gusticollis. Photograph by M. V. S. 









Vescicating Insects 


55 


While blister beetles have been especially used for external applica¬ 
tion, they are also at times used internally as a stimulant and a 
diuretic. The powder or extract was formerly much in vogue as an 
aphrodisiac, and formed the essential constituent of various philters, 
or “love powders”. It is now known that its effects on the reproduc¬ 
tive organs appear primarily after the kidneys have been affected to 
such an extent as to endanger life, and that many cases of fatal poison 
have been due to its ignorant use. 

There are many cases on record of poisoning and death due to 
internal use, and in some instances from merely external application. 
There are not rarely cases of poisoning of cattle from feeding on 
herbage bearing a large number of the beetles and authentic cases are 
known of human beings who have been poisoned by eating the flesh 
of such cattle. Robert states that the beetles are not poisonous to 
birds but that the flesh of birds which have fed on them is poisonous 
to man, and that if the flesh of chickens or frogs which have fed on 
the cantharidin be fed to cats it causes in them the same symptoms 
as does the cantharidin. 

Treatment of cases of cantharidin poison is a matter for a skilled 
physician. Until he can be obtained, emetics should be administered 
and these should be followed by white of egg in water. Oils should 
be avoided, as they hasten the absorption of the poison. 

Other Cryptotoxic Insects —Though the blister beetles are the 
best known of the insects with poisonous blood plasma, various 
others have been reported and we shall refer to a few of the best 
authenticated. 

One of the most famous is the Chrysomelid beetle, Diamphidia 
simplex , the bod) 7 fluids of whose larvae are used by certain South 
African bushmen as an arrow poison. Its action is due to the presence 
of a toxalbumin which exerts a haemolytic action on the blood, and 
produces inflammation of the subcutaneous connective tissue and 
mucous membranes. Death results from general paralysis. Krause 
(1907) has surmised that the active principle may be a bacterial toxine 
arising from decomposition of the tissues of the larva, but he presents 
no support of this view and it is opposed by all the available evidence. 

In China, a bug, Heuchis sanguined, belonging to the family 
Cicadidfe, is used like the Meloidas, to produce blistering, and often 
causes poisoning. It has been assumed that its vescicating properties 
are due to cantharidin, but the presence of this substance has not 
been demonstrated. 


Poisonous Arthropods 


56 


Certain Aphididae contain a strongly irritating substance which 
produces, not merely on mucous membranes but on outer skin, a 
characteristic inflammation. 

It has been frequently reported that the larvae of the Eurpoean 
cabbage butterfly, Pieris brassiere, accidentally eaten by cows, horses, 
ducks, and other domestic animals, cause severe colic, attempts to 
vomit, paralysis of the hind legs, salivation, and stomatitis. On 
postmortem there are to be found haemorrhagic gastro-enteritis, 
splenitis, and nephritis. Kobert has recently investigated the subject 
and has found a poisonous substance in the blood of not only the 
larvae but also the pupae. 


CHAPTER III 


PARASITIC ARTHROPODA AFFECTING MAN 

The relation of insects to man as simple parasites has long been 
-studied, and until very recent years the bulk of the literature of medi¬ 
cal entomology referred to this phase of the subject. This is now 
completely overshadowed by the fact that so many of these parasitic 
forms are more than simple parasites, they are transmitters of other 
microscopic parasites which are pathogenic to man. Yet the impor¬ 
tance of insects as parasites still remains and must be considered in a 
discussion of the relation of insects to the health of man. In taking 
up the subject we shall first consider some general features of the 
phenomenon of animal parasitism. 

Parasitism is an adaptation which has originated very often among 
living organisms and in widely separated groups. It would seem 
simple to define what is meant by a “parasite” but, in reality, the 
term is not easily limited. It is often stated that a parasite is “An 
organism which lives at the expense of another,” but this definition 
is applicable to a predatory species or, in its broadest sense, to all 
organisms. For our purpose we may say with Braun: “A parasite 
is an organism which, for the purpose of obtaining food, takes up its 
abode, temporarily or permanently, on or within another living 
organism”. 

Thus, parasitism is a phase of the broad biological phenomenon of 
symbiosis , or living together of organisms. It is distinguished from 
mutualism, or symbiosis in the narrow sense, by the fact that only one 
party to the arrangement obtains any advantage, while the other is 
to a greater or less extent injured. 

Of parasites we may distinguish on the basis of their location on or 
in the host, ecto-parasites, which live outside of the body; and endo- 
parasites, which live within the body. On account of their method 
of breathing the parasitic arthropods belong almost exclusively to the 
first of these groups. 

On the basis of relation to their host, we find temporary parasites, 
those which seek the host only occasionally, to obtain food; and the 
stationary or permanent parasites which, at least during certain stages, 
do not leave their host. 

Facultative parasites are forms which are not normally parasitic, 
but which, when accidentally ingested, or otherwise brought into the 


58 


Parasitic Arthropods 


body, are able to exist for a greater or less period of time in their 
unusual environment. These are generally called in the medical 
literature “pseudoparasites” but the term is an unfortunate one. 

We shall now take up the different groups of arthropods, discussing 
the more important of the parasitic forms attacking man. The 
systematic relationship of these forms, and key for determining 
important species will be found in Chapter XII. 

Acarina or Mites 

The Acarina, or mites , form a fairly natural group of arachnids, 
characterized, in general, by a sac-like, unsegmented body which is 
generally fused with the cephalothorax. The mouth-parts have been 
united to from a beak or rostrum. 

The representatives of this group undergo a marked metamor¬ 
phosis. Commonly, the larvae on hatching from the egg, possess but 
three pairs of legs, and hence are called hexapod larvae. After a molt, 
they transform into nymphs which, like the adult, have four pairs of 
legs and are called octopod nymphs. These after a period of growth, 
molt one or more times and, acquiring external sexual organs, become 
adult. 

Most of the mites are free-living, but there are many parasitic 
species and as these have originated in widely separated families, the 
Acarina form an especially favorable group for study of the origin of 
parasitism. Such a study has been made by Ewing (1911), who has 
reached the following conclusions: 

“We have strong evidence indicating that the parasitic habit has 
originated independently at least eleven times in the phvlogeny of the 
Ararina. Among the zoophagous parasites, the parasitic habit has 
been developed from three different types of free-living Acarina: 
(a) predaceous forms, (b) scavengers, (c) forms living upon the juices 
of plants.” 

Ewing also showed that among the living forms of Acarina we can 
trace out ah the stages of advancing parasitism, semiparasitism, 
facultative parasitism, even to the fixed and permanent type, and 
finally to cndoparasitism. 

Of the many parasitic forms, there are several species which are 
serious parasites of man and we shall consider the more important of 
these. Infestation by mites is technically known as acariasis. 


A carina, or Mites 


59 



43. Effect of the harvest mites on the skin of man. Photograph by 
J. C. Bradley. 






■6o 


Parasitic Arthropods 


The Trombidiidae, or Harvest Mites 

In many parts of this country it is impossible for a visitor to go 
into the fields and, particularly, into berry patches and among tall 
weeds and grass in the summer or early fall without being affected by 
an intolerable itching, which is followed, later, by a breaking out of 
wheals, or papules, surrounded by a bright red or violaceous aureola, 
(fig. 43). It is often regarded as a urticaria or eczema, produced by 
change of climate, an error in diet, or some condition of general health. 

Sooner or later, the victim finds that it is due to none of these, but 
to the attacks of an almost microscopic red mite, usually called 
"“jigger” or “chigger” in this country. As the term “chigger” is 
applied to one of the true fleas, Dermatophilus penetrans, of the tropics, 

these forms are more 
correctly known as 
“harvest mites.” 
N atives of an infested 
region may be so 

immune or accus¬ 

tomed to its attacks 
as to be unaware of 
its presence, though 
such immunity is by 
no means possessed 
by all who have been 

44. Harvest mites. (Larvae of Trombidium). After C. V. , " , . .. 

Riley. long exposed to the 

annoyance. 

The harvest mites, or chiggers, attacking man are larval forms, 
possessing three pairs of legs (fig. 44). Their systematic position was 
at first unknown and they were classed under a special genus Leptus, 
a name which is very commonly still retained in the medical literature. 
It is now known that they are the larval forms of various species of 
the genus Trombidium, a group of predaceous forms, the adults of 
which feed primarily on insects and their eggs. In this country the 
species best known are those to be found late in summer, as larvae 
at the base of the wings of houseflies or grasshoppers. 

There is much uncertainty as to the species of the larvae attacking 
man but it is clear that several are implicated. Bruvant has shown 
that in France the larvae Trombidium inapinatum and Trombidium 
holosericeum are those most frequently found. The habit of attacking 
man is abnormal and the larvae die after entering the skin. Normally 
they are parasitic on various insects. 




The Harvest Mites 


61 

Most recent writers agree that, on man, they do not bore into the 
skin, as is generally supposed, but enter a hair follicle or sebaceous 
gland and from the bottom of this, pierce the cutis with their elongate 
hypopharynx. According to Braun, there arises about the inserted 
hypopharynx a fibrous secretion — the so-called “beak” which is, in 
reality, a product of the host. Dr. J. C. Bradley, however, has made 
careful observations on their method of attack, and he assures us that 
the mite ordinarily remains for a long time feeding on the surface of 
the skin, where it produces the erythema above described. During 
this time it is not buried in the skin but is able to retreat rapidly into 
it through a hair follicle or sweat gland. The irritation from the 
mites ceases after a few days, but not infrequently the intolerable 
itching leads to so much scratching that secondary infection follows. 

Relief from the irritation may be afforded by taking a warm salt 
bath as soon as possible after exposure or by killing the mites by 
application of benzine, sulphur ointment or carbolized vaseline. 
When they are few in number, they can be picked out with a sterile 
needle. 

Much may be done in the way of warding off their attacks by 
wearing gaiters or close-woven stockings extending from ankle to the 
knee. Still more efficacious is the sprinkling of flowers of sulphur in 
the stockings and the underclothes from a little above the knee, down. 
The writers have known this to make it possible for persons who were 
especially susceptible to work with perfect comfort in badly infested 
regions. Powdered naphthalene is successfully used in the same way 
and as Chittenden (1906) points out, is a safeguard against various 
forms of man-infesting tropical insect pests. 

The question of the destruction of the mites in the field is some¬ 
times an important one, and under some conditions, is feasible. 
Chittenden states that much can be accomplished by keeping the 
grass, weeds, and useless herbage mowed closely, so as to expose the 
mites to the sun. He believes that in some cases good may be done 
by dusting the grass and other plants, after cutting, with flowers of 
sulphur or by spraying with dilute kerosene emulsion in which 
sulphur has been mixed. More recently (1914) he calls attention to 
the value of cattle, and more especially sheep, in destroying the pests 
by tramping on them and by keeping the grass and herbage closely 
cropped. 


62 


Parasitic Arthropods 
IxODOIDEA OR TlCKS 


Until recently, the ticks attracted comparatively little attention 
from entomologists. Since their importance as carriers of disease 

has been established, interest in 
the group has been enormously 
stimulated and now they rank 
second only to the mosquitoes 
in the amount of detailed study 
that has been devoted to them. 

The ticks are the largest of 
the Acarina. They are char¬ 
acterized by the fact that the 
hypostome, or “tongue” (fig. 45) 
is large and file-like, roughened 
by sharp teeth. They possess 
a breathing pore on each side 
of the body, above the third 
or fourth coxae (fig. 45 b). 

There are two distinct fami¬ 
lies of the Ixodoidea, differing 
greatly m structure, lite-history and habits. These are the Argasidae 
and the Ixodidae. We shall follow Nuttall (1908) in characterizing 
these two families and in pointing out their biological differences, and 
shall discuss briefly the more important species which attack man. 
The consideration of the 
ticks as carriers of disease 
will be reserved for a later 
chapter. 

Argasidae 

In the ticks belonging to 
the family Argasidae, there 
is comparatively little sexual 
dimorphism, while this is 
very marked in the Ixodidae. 

The capitulum, or so-called 
“head” is ventral, instead of 
terminal; the palpi are leg¬ 
like, with the segments subequal; the scutum, or dorsal shield, is 
absent; eyes, when present, are lateral, on supracoxal folds. The 




45 a. Argus persicus. Capitulum of male 
After Nuttall and Warburton. 












Ixodoidea, or Ticks 63 

spiracles are very small; coxae unarmed; tarsi without ventral spurs, 
and the pul villi are absent or rudimentary. 

In habits and life history' the Argasidae present striking characteris¬ 
tics. In the first place, they are long-lived, a factor which counts for 
much in the maintenance of the species. They are intermittent 
feeders, being comparable with the bed-bug in this respect. There are 
two or more nymphal stages, and they may* molt after attaining matu¬ 
rity. The female lays comparatively' few eggs in several small batches. 

Nuttall (1911) concludes that “The Argasidae represent the rela¬ 
tively^ primitive type of ticks because they' are less constantly para- 



46. Argus persicus. Dorsal and ventral aspects. (X 4). After Hassell. 


sitic than are the Ixodidae. Their ny'mphs and adults are rapid 
feeders and chiefly' infest the habitat of their hosts. * * * Owing 

to the Argasidas infesting the habitats of their hosts, their resistance 
to prolonged starvation and their rapid feeding habits, they do not 
need to bring forth a large progeny', because there is less loss of life 
in the various stages, as compared with the Ixodidae, prior to their 
attaining maturity.’’ 

Of the Argasidae, we have in the United States, several species 
which have been reported as attacking man. 

Argas persicus, the famous “Miana bug’’ (fig. 46), is a very widely 
distributed species, being reported from Europe, Asia, Africa, and 
Australia. It is every "where preeminently a parasite of fowls. 




64 


Parasitic Arthropods 


According to Nuttall it is specifically identical with Argas americanus 
Packard or Argas miniatus Koch, which is commonly found on fowls- 

in the United States, in the South 
and Southwest. Its habits are com¬ 
parable to those of the bed-bug. It 
feeds intermittently, primarily at 
night, and instead of remaining on its 
host, it then retreats to cracks and 
crevices. Hunter and Hooker (1908) 
record that they have found the larva 
to remain attached for five or eight 
days before dropping. Unlike the 
Ixodidae, the adults oviposit fre¬ 
quently. 

The most remarkable feature of 

the biology of this species is the great 

47 . Otiobius (Ornithodoros) megnini, head longevity, especially of the adult, 
of nymph. After Stiles. & J ^ J 

Hunter and Hooker report keeping 
larvae confined in summer in pill boxes immediately after hatch¬ 
ing for about two months while under similar conditions those 
of the Ixodid, Boophilus annulatus lived for but two or three days. 




48. Otiobius (Ornithodoros) megnini, male, (a) dorsal, (6) ventral 
aspect. After Nuttall and Warburton. 


Many writers have recorded keeping adults for long periods without 
food. We have kept specimens in a tin box for over a year and a half 
and at the end of that time a number were still alive. Laboullicne 
kept unfed adults for over three years. In view of the effectiveness of 







Ixodoidea , or Ticks 


65 


sulphur in warding off the attacks of Trombidiidae, it is astonishing 
to find that Lounsbury has kept adults of Argas persicus for three 
months in a box nearly filled with flowers of sulphur, with no apparent 
effect on them. 

We have already called attention to the occasional serious effects 
of the bites of this species. While such reports have been frequently 
discredited there can be no doubt that they have foundation in fact. 
The readiness with which this tick attacks man, and the extent to 
which old huts may be infested makes it especially troublesome. 

Otiobius ( Ornithodoros) megnini, the “spinose ear-tick ’’(figs. 47,48), 
first described from Mexico, as occurring in the ears of horses, is a 
common species in our Southwestern States and is recorded by Banks 
as occurring as far north as Iowa. 

The species is remarkable for the great difference between the 
spiny nymph stage and the adult. The life history has been worked 
out by Hooker (1908). Seed ticks, having gained entrance to the 
ear, attach deeply down in the folds, engorge, and in about five days, 
molt; as nymphs with their spinose body they appear entirely unlike 
the larvae. As nymphs they continue feeding sometimes for months. 
Finally the nymph leaves the host, molts to form the unspined adult, 
and without further feeding is fertilized and commences oviposition. 

The common name is due to the fact that in the young stage the 
ticks occur in the ear of their hosts, usually horses or cattle. Not 
uncommonly it has been reported as occurring in the ear of man and 
causing very severe pain. Stiles recommends that it be removed by 
pouring some bland oil into the ear. 

Banks (1908) reports three species of Ornithodoros — O. turicata, 
coriaceus and talaje —as occurring in the United States. All of these 
attack man and are capable of inflicting very painful bites. 

Ixodidae 

The ticks belonging to the family Ixodidae (figs. 49 and 50) exhibit 
a marked sexual dimorphism. The capitulum is anterior, terminal, 
instead of ventral as in the Argasidae; the palpi are relatively rigid 
(except in the subfamily Ixodinae), with rudimentary fourth segment; 
scutum present; eyes, when present, dorsal, on side of scutum. The 
spiracles are generally large, situated well behind the fourth coxae; 
coxae generally with spurs; pulvilli always present. 

In habits and life history the typical Ixodidae differ greatly from 
the Argasidae. They are relatively short-lived, though some recent 


66 


Parasitic Arthropods 


work indicates that their long¬ 
evity has been considerably 
under-estimated. Typically, 
they are permanent feeders, 
remaining on the host, or hosts, 
during the greater part of their 
life. They molt twice only, 
on leaving the larval and the 
nymphal stages. The adult 
female deposits a single, large 
batch of eggs. Contrasting 
the habits of the Ixodidae to 
those of the Argasidae, Nuttall 
(1911) emphasizes that the 
Ixodidae are more highly 
specialized parasites. “The 
majority are parasitic on hosts 
having no fixed habitat and 
consequently all stages, as a 
rule, occur upon the host.” 

As mere parasites of man, apart from their power to transmit 
disease, the Ixodidae are much less important than the Argasidae. 
Many are reported as occasionally attacking man and of these the 
following native spe¬ 
cies may be mentioned. 

Ixodes ricinus, the 
European castor bean 
tick (figs. 49, 50), is a 
species which has been 
often reported from 
this country but Banks 
(1908) lias shown that, 
though it does occur, 
practically all of the 
records apply to Ixodes 
scapularis or Ixodes 
cookei. In Europe, 

Ixodes ricinus is very 
abundant and very 
commonly attacks 




50. Ixodes ricinus, var. scapularis, female. Capitulum and 
scutum; ventral aspect of capitulum- coxse; tarsus 4; 
spiracle; genital and anal grooves. After Nuttall and 
Warburton. 














Ixodoidea, or Ticks 


67 


man. At the point of penetration of the hypostome there is more or 
less inflammation but serious injury does not occur unless there have 
been introduced pathogenic bacteria or, unless the tick has been 
abruptly removed, leaving the capitulum in the wound. Under the 
latter circumstances, there maybe an abscess formed about the foreign 
body and occasionally, serious results have followed. Under certain 
conditions the tick, in various stages, may penetrate under the skin 
and produce a tumor, within which it may survive for a considerable 
period of time. 

Ixodes cookei is given by Banks as “common on mammals in the 
Eastern States as far west as the Rockies.” It is said to affect man 
severely. 

Amblyomma americanwn, (fig. 158c), the “lone star tick,” is 
widely distributed in the United States. Its common name is derived 
from the single silvery spot on the scutum of the female. Hunter 
and Hooker regard this species as, next to Boophilus annulatus, the 
most important tick in the United States. Though more common on 
cattle, it appears to attack mammals generally, and “in portions of 
Louisiana and Texas it becomes a pest of considerable importance to 
moss gatherers and other persons who spend much time in the forests.” 

Amblyomma cajennense, noted as a pest of man in central and 
tropical America, is reported from various places in the south and 
southwestern United States. 

Dermacentor variabilis is a common dog tick of the eastern United 
States. It frequently attacks man, but the direct effects of its bite 
are negligible. 

The “ Rocky Mountian spotted fever tick” ( Dermacentor andersoni 
according to Stiles, D. venustus according to Banks) is, from the view¬ 
point of its effects on man, the most important of the ticks of the 
United States. This is because, as has been clearly established, it 
transmits the so-called “spotted fever” of man in our northwestern 
states. This phase of the subject will be discussed later and it need 
merely be mentioned here, that this species has been reported as 
causing painful injuries by its bites. Dr. Stiles states that he has 
seen cases of rather severe lymphangitis and various sores and swell¬ 
ings developing from this cause. In one case, of an individual bitten 
near the elbow, the arm became very much swollen and the patient 
was confined in bed for several days. The so-called tick paralysis 
produced by this species is discussed in a preceding chapter. 


68 


Parasitic Arthropods 


There are many other records of various species of ticks attacking 
man, but the above-mentioned will serve as typical and it is not neces¬ 
sary to enter into greater detail. 

Treatment of Tick Bites —When a tick attaches to man the first 
thing to be done is to remove it without leaving the hypostome in the 
wound to fester and bring about secondary effects. This is best 
accomplished by applying to the tick’s body some substance which 
will cause it to more readily loosen its hold. Gasoline or petroleum, 


oil or vaseline will serve. 
For removing the 
spinose ear-tick, Stiles 
recommends pouring 
some bland oil into the 
ear. Others have used 
effectively a pledget of 
cotton soaked in chloro¬ 
form. 



In general, the treat¬ 
ment recommended by 
Wellman for the bites 
of Ornithodoros moubata 
vail prove helpful. It 
consists of prolonged 
bathing in very hot 
water, followed by the 


51 . Dermanyssus gallinae. female. After Delafond. application of a Strong 


solution of bicarbonate 


of soda, which is allowed to dry upon the skin. He states that this 
treatment is comforting. For severe itching he advises smearing 
the bites with vaseline, which is slightly impregnated with camphor 
or menthol. Medical aid should be sought when complications arise. 

The Dermanyssidae are Gamasid mites which differ from others of 
the group in that they are parasitic on vertebrates. None of the 
species normally attack man, but certain of them, especially the 
poultry mite, may be accidental annoyances. 

Dermanyssus gallince (fig. 51), the red mite of poultry, is an exceed¬ 
ingly common and widespread parasite of fowls. During the day 
it lives in cracks and crevices of poultry houses, under supports of 
roosts, and in litter of the food and nests, coming out at night to feed. 






Tarsonemidce 


69 


They often attack people working in poultry houses or handling and 
plucking infested fowls. They may cause an intense praritis, but they 

do not produce a true dermatosis, for 
they do not find conditions favorable for 
multiplication on the skin of man. 

Tarsonemidae 

The representatives of the family Tar¬ 
sonemidae are minute mites, with the body 
divided into cephalothorax and abdomen. 
There is marked sexual dimorphism. 
The females possess stigmata at the 
anterior part of the body, at the base of 
the rostrum, and differ from all other mites 
in having on each side, a prominent clavate 
organ between the first and second legs. 
52 ' P ma^ loi AfLr V Webs C t°er US ’ fe " The l arva > when it exists, is hexapodous 

and resembles the adult. A number of the 
species are true parasites on insects, while others attack plants. 
Several of them may be accidental parasites of man. 

Pediculoides ventricosus 
(fig. 52 and 53) is, of all the 
Tarsonemidae reported, the 
one which has proved most 
troublesome to man. It is a 
predaceous species which 
attacks a large number of 
insects but which has most 
commonly been met with by 
man through its fondness for 
certain grain-infesting insects, 
notably the Angoumois grain 
moth, Sitotroga cerealella, and 
the wheat straw-worm, Iso¬ 
soma grande. In recent years 
it has attracted much atten¬ 
tion in the United States and 
its distribution and habits 
have been the object of detail- 

W,, T_/ _ \ 53. Pediculoides ventricosus, gravid female. (X SO) 

Study by Webster (1901). After Webster. 






70 


Parasitic Arthropods 


There is a very striking sexual dimorphism in this species. The 
non-gravid female is elongate, about 2009, by yojx (fig. 52), with the 
abdomen slightly striated longitudinally. The gravid female (fig. 53) 
has the abdomen enormously swollen, so that it is from twenty to a 
hundred times greater than the rest of the body. The species is- 
viviparous and the larva' undergo their entire growth in the body of 
the mother. They emerge as sexually mature males and females 
which soon pair. The male (fig. 54) is much smaller, reaching a 

length of only 3 20^ but 
is relatively broad, 
8c| jl, and angular. Its 
abdomen is very great¬ 
ly reduced. 

As far back as 1850 
it was noted as caus¬ 
ing serious outbreaks 
of peculiar dermatitis 
among men handling 
infested grain. For 
some time the true 
source of the difficulty 
was unknown and it 
was even believed that 
the grain had been 
poisoned. Webster 
has shown that in this 
country (and probably 
in Europe as well) its 
attacks have been mistaken for those of the red bugs or “chiggers” 
(larval Trombiidse). More recently a number of outbreaks of a 
mysterious “skin disease” were traced to the use of straw mattresses, 
which were found to be swarming with these almost microscopic 
forms which had turned their attentions to the occupants of the beds. 
Other cases cited were those of farmers running wheat through a 
fanning mill, and of thrashers engaged in feeding unthrashed grain 
into the cylinder of the machine. 

The medical aspects of the question have been studied especially 
by Schamberg and Goldbergcr and from the latter’s summary (1910) 
we derive the following data. Within twe ve to sixteen hours after 
exposure, itching appears and in severe cases, especially where expo- 





Pediculoides Ventricosus 


7 i 


sure is continued night after night by sleeping on an infested bed, the 
itching may become almost intolerable. Simultaneously, there 
appears an eruption which characteristically consists of wheals 
surrounded by a vesicle (fig. 55). The vesicle as a rule does not exceed 
a pin head in size but may become as large as a pea. Its contents 



55. Lesions produced by the attacks of Pediculoides ventri- 
cosus. After Webster. 


rapidly become turbid and in a few hours it is converted into a pustule. 
The eruption is most abundant on the trunk, slight on the face and 
extremities and almost absent on the feet and hands. In severe cases 
there may be constitutional disturbances marked, at the outset, by 
chilliness, nausea, ajid vomiting, followed for a few days by a slight 
elevation of temperature, with the appearance of albumin in the 
urine. In some cases the eruption may simulate that of chicken-pox 
or small-pox. 







72 


Parasitic Arthropods 


Treatment for the purpose of killing the mites is hardly necessary 
as they attach feebly to the surface and are readily brushed off by 
friction of the clothes. “Antipruritic treatment is always called for; 
warm, mildly alkaline baths or some soothing ointment, such as zinc 
oxide will be found to fulfil this indication.’’ Of course, reinfestation 
must be guarded against, by discarding, or thoroughly fumigating 
infested mattresses, or by avoiding other sources. Goldberger sug¬ 
gests that farm laborers who must work with infested wheat or straw 
might protect themselves by anointing the body freely with some 
bland oil or grease, followed by a change of clothes and bath as soon 
as their work is done. We are not aware of any experiments to 
determine the effect of flowers of sulphur, but their efficiency in the 
case of “red bugs” suggests that they are worth a trial against 
Pediculoides. 

Various species of Tyroglyphidae (fig. 150/) may abound on dried 
fruits and other products and attacking persons handling them, may 
cause a severe dermatitis, comparable to that described above for 
Pediculoides ventricosus. Many instances of their occurrence as such 
temporary ectoparasites are on record. Thus, workers who handle 
vanilla pods are subject to a severe dermatitis, known as vanillism, 
which is due to the attacks of Tyroglyphus siro, or a closely related 
species. The so-called “grocer’s itch” is similarly caused by mites 
infesting various products. Castellani has shown that in Ceylon, 
workers employed in the copra mills, where dried cocoanut is ground 
up for export, are much annoyed by mites, which produce the so-called 
“copra itch.” The skin of the hands, arms and legs, and sometimes 
of the whole body, except the face,is covered by fairly numerous, very 
pruriginous papules, often covered by small, bloody crusts due to 
scratching. The condition is readily mistaken for scabies. It is 
due to the attacks of Tyroglyphus longior castellanii which occur in 
enormous numbers in some samples of the copra. 

Sarcoptidae 

The Sarcoptidae are minute whitish mites, semi-globular in shape, 
with a delicate transversely striated cuticula. They lack eyes and 
tracheae. The mouth-parts are fused at the base to form a cone 
which is usually designated as the head. The legs are short and 
stout, and composed of five segments. The tarsi may or may not 
possess a claw and may terminate in a pedunculated sucker, or simple 
long bristle, or both. The presence or absence of these structures 


Sarcoptidce, or Itch Mites 


73 


and their distribution are much used in classification. The mites 
live on or under the skin of mammals and birds, where they produce 

the disease known as scabies, mange, or 
itch. Several species of the Sarcoptidae 
attack man but the most important of 
these, and the one pre-eminent as the 
“itch mite” is Sarcoptes scabiei. 

The female of Sarcoptes scabiei, of man, 
is oval and yellowish white; the male 
more rounded and of a somewhat reddish 
tinge, and much smaller. The body is 
marked by transverse stria? which are 
partly interrupted on the back. There 
are transverse rows of scales, or pointed 
spines, and scattered bristles on the 
dorsum. 

The male (fig. 56) which is from 200- 
240^ in length, and 150-200^ in breadth, 
possesses pedunculated suckers on each 
pair of legs except the third, which bears, instead, a long bristle. 
The female (fig. 56) 300-450^ in length and 2 5 o-3SO[a in breadth, has 
the pedunculated suckers on the first and second pairs of legs, only, 
the third and fourth terminating in bristles. 

The mite lives in irregular galleries from 
a few millimeters to several centimeters in 
length, which it excavates in the epidermis 
(fig. 57). It works especially where the 
skin is thin, such as between the fingers, 
in the bend of the elbows and knees, and 
in the groin, but it is by no means restricted 
to these localities. The female, alone, 
tunnels into the skin; the males remain 
under the superficial epidermal scales, and 
seldom are found, as they die soon after 
mating. 

As she burrows into the skin the female 
deposits her eggs, which measure about 
150 x 100^. Fiirstenberg says that each 
deposits an average of twenty-two to twenty-four eggs, though 
Guddcn reports a single burrow as containing fifty-one. From these 




56a. Sarcoptes scabiei, male. 

(X 100). After Fiirsten- 
berg. 




74 


Parasitic Arthropods 


there develop after about seven days, the hexapod larvas. These 
molt on the sixteenth day to form an octopod nymph, which molts 
again the twenty-first day. At the end of the fourth week the 
nymphs molt to form the sexually mature males and the so-called 
pubescent females. These pair, the males die, and the females again 
cast their skin, and become the oviparous females. Thus the life¬ 
cycle is completed in about twenty-eight days. 

The external temperature exercises a great influence on the develop¬ 
ment of the mites and thus, during the winter, the areas of infesta¬ 
tion not only do not spread, but they become restricted. As soon as 
the temperature rises, the mites increase and the infestation becomes- 
much more extensive. 



57. Sarcoptes scabiei. Diagrammatic representation of the course in 
the skin of man. 


In considering the possible sources of infestation, and the chances- 
of reinfestation after treatment, the question of the ability of the mite 
to live apart from its host is a very important one. Unfortunately,, 
there are few reliable data on this subject. Gerlach found that, 
exposed in the dry, warm air of a room they became very inactive 
within twenty-four hours, that after two days they showed only 
slight movement, and that after three or four days they could not 
be revived by moisture and warming. The important fact was 
brought out that in moist air, in folded soiled underwear, they sur¬ 
vived as long as ten days. Bourguignon found that under the most 
favorable conditions the mites of Sarcoptes scabiei equi would live for 
sixteen days. 

The disease designated the “itch” or “scabies,” in man has been 
known from time immemorial, but until within less than a hundred 
years it was almost universally attributed to malnutrition, errors of 














Sarcoptidce , or Itch Mites 


75 


diet, or ‘‘bad blood.” This was in spite of the fact that the mite was 
known to Mouffet and that Bonomo had figured both the adult and 
the egg and had declared the mite the sole cause of the disease. In 
1834 the Corsican medical student, Francis Renucci, demonstrated 
the mite before a clinic in Saint Louis Hospital in Paris and soon 
thereafter there followed detailed studies of the life history of the 

various itch mites of 
man and animals. 

The disease is a cos¬ 
mopolitan one, being ex¬ 
ceedingly abundant in 
some localities. Its 
spread is much favored 
where large numbers of 
people are crowded to¬ 
gether under insanitary 
conditions and hence it 
increases greatly during 
wars and is widely dis¬ 
seminated and abundant 
immediately afterwards. 
Though more commonly 
to be met with among 
the lower classes, it not 
infrequently appears 
among those of the most 
cleanly, careful habits, 
and it is such cases that 
are most liable to wrong 
diagnosis by the physi¬ 
cian. 

Infection occurs solely through the passage, direct or indirect, 
of the young fertilized females to the skin of a healthy individual. 
The adult, oviparous females do not quit their galleries and hence 
do rot serve to spread the disease. The young females move about 
more or less at night and thus the principal source of infestation is 
through sleeping in the same bed with an infested person, or indirectly 
through bedclothes, or even towels or clothing. Diurnal infestation 
through contact or clothing is exceptional. Many cases are known 
of the disease being contracted from animals suffering from scabies, 
or mange. 



08 . Scabies on the hand. From portfolio of Dermo- 
chromes by permission of Rebman & Co., of 
New York. Publisheis. 



7 6 


Parasitic Arthropods 



When a person is exposed to infestation, the trouble manifests 
itself after eight or ten days, though there usually elapses a period of 

twenty to thirty days be¬ 
fore there is a suspicion of 
anything serious. The first 
symptom is an intense 
itching which increases 
when the patient is in bed. 
When the point of irrita¬ 
tion is examined the gal¬ 
leries may usually be seen 
as characteristic sinuous 
lines, at first whitish in 
color but soon becoming 
blackish because of the con¬ 
tained eggs and excrement. 
The galleries, which may 
not be very distinct in 
some cases, may measure 
as much as four centi¬ 
meters in length. Little 
vesicles, of the size of a 

59. Scabies on the hand. After Duhring. . , . . , . 

pm head are produced by 
the secretions of the feeding mite; they are firm, and projecting, and 
contain a limpid fluid. Figures 58 
and 59 show the typical appearance 
of scabies on the hands, while figure 
60 shows a severe general infesta¬ 
tion. The intolerable itching induces 
scratching and through this various 
complications may arise. The lesions 
are not normally found on the face 
and scalp, and are rare on the back. 

Formerly, scabies was considered 
a very serious disease, for its cause 
and method of treatment were un¬ 
known, and potentially it may con¬ 
tinue indefinitely. Generation after 
generation of the mites may develop 

and finally their number become so After Morrow. 













Sarcoptidce, or Itch Mites 


77 


great that the general health of the individual is seriously affected. 
Now that the true cause of the disease is known, it is easily con¬ 
trolled. 

Treatment usually consists in softening the skin by friction with 
soap and warm water, followed by a warm bath, and then applying 
some substance to kill the mites. Stiles gives the following direc¬ 
tions, modified from Bourguignon’s, as “a rather radical guide, to 
be modified according to facilities and according to the delicacy of the 
skin or condition of the patient”: 

i. The patient, stripped naked, is energetically rubbed all over 
(except the head) for twenty minutes, with green soap and warm 
water. 2. He is then placed in a warm bath for thirty minutes, 
during which time the rubbing is continued. 3. The parasiticide 
is next nibbed in for twenty minutes and is allowed to remain on the 
body for four or five hours; in the meantime the patient’s clothes are 
sterilized, to kill the eggs or mites attached to them. 4. A final 
bath is taken to remove the parasiticide. 

The parasiticide usually relied on is the officinal sulphur ointment 
of the United States pharmacopoeia. When infestation is severe it 
is necessary to repeat treatment after three or four days in order 
to kill mites which have hatched from the eggs. 

The above treatment is too severe for some individuals and may, 
of itself, produce a troublesome dermatitis. We have seen cases 
where the treatment was persisted in and aggravated the condi¬ 
tion because it was supposed to be due to the parasite. For deli¬ 
cate-skinned patients the use of balsam of Peru is very satisfac¬ 
tory, and usually causes no irritation whatever. Of course, sources 
of reinfection should be carefully guarded against. 

Sarcoptes scabiei crustosce, which is a distinct variety, if not species, 
of the human itch mite, is the cause of so-called Norwegian itch. 
This disease is very contagious, and is much more resistant than the 
ordinary scabies. Unlike the latter, it may occur on the face and 
scalp. 

Sarcoptes scabiei not only attacks man but also occurs on a large 
number of mammals. Many species, based on choice of host, and 
minute differences in size and secondary characters, have been 
established, but most students of the subject relegate these to 
varietal rank. Many of them readily attack man, but they have 
become sufficiently adapted to their normal host so that they are 
usually less persistent on man. 


78 


Parasitic Arthropods 


Notoedres cati (usually known as Sarcoptes minor) is a species 
of itch mites which produce an often fatal disease of cats. The body 
is rounded and it is considerably smaller than Sarcoptes scabiei , 
the female (fig. 61) measuring 215-230^ long and 165- 175^ wide; 
the males 145-150^ by 120-125^. The most important character 



61. Notoedres cati, male and female. After Railliet. 


separating Notoedres from Sarcoptes is the position of the anus, 
which is dorsal instead of terminal. The mite readily transfers 
to man but does not persist, the infestation usually disappearing 


spontaneously in about two weeks. Infested cats are 
very difficult to cure, unless treatment is begun at 



the very inception of the outbreak, and under ordi¬ 


nary circumstances it is better to kill them promptly, 
to avoid spread of the disease to children and others 
who may be exposed. 


Demodecidae 


The Demodecidae are small, elongate, vermiform 
mites which live in the hair follicles of mammals. 
The family characteristics will be brought out in the 
discussion of the species infesting man, Demodex 
folliculorum. 


Demodex folliculorum (fig. 62) is to be found very 
commonly in the hair follicles and sebaceous glands 
of man. It is vermiform in appearance, and with the 
elongate abdomen transversely striated so as to give 


62 . Demodex foiii- it the appearance of segmentation. The female is 380- 
Af tef 11 bi ar! ch ard! 400[A long by 45 ^; the male 300^ by 40^. The three- 









Demodecidce, or Hair-follicle Mites 


79 


jointed legs, eight in number, are reduced to mere stubs in the adult. 
The larval form is hexopod. These mites thus show in their form a 
striking adaptation to their environment. In the sebaceous glands 



Mtyzva d*J hth Jap Ercfvtt .Arts 

Demode* follieulorum ( Owen ) 


63. Demodex follieulorum. Section through skin showing the 
mites in situ. Magnification of Nos. 1, 2, 6 and 7, X 150; 

Nos. 3 4, 5, X 450. After Megnin. 

and hair follicles they lie with their heads down (fig. 63). Usually 
there are only a few in a gland, but Gruby has counted as many as 
two hundred. 

The frequency with which they occur in man is surprising. Ac¬ 
cording to European statistics they are found in 50 per cent to 60 per 
cent or even more. Gruby found them in forty out of sixty persons 






So 


Pa rasitic A rth ropods 


examined. These figures arc very commonly quoted, but reliable 
data for the United States seem to be lacking. Our studies indicate 
that it is very- much less common in this country than is generally 
assumed. 

The Demodex in man does not, as a rule, cause the slightest 
inconvenience to its host. It is often stated that they give rise to 
comedons or “black-heads” but there is no clear evidence that they 
are ever implicated. Certain it is that they are not the usual cause. 
A variety of the same, or a very closely related species of Demodex, 
on the dog gives rise to the very resistant and often fatal follicular 
mange. 

Hexapoda or True Insects 

The Hexapoda, or true insects, arc characterized by the fact that 
the adidt possesses three pairs of legs. The body is distinctly 
segmented and is divided into head, thorax, and abdomen. 

The mouth-parts in a generalized form, consist of an upper lip, 
or labrum, which is a part of the head capsule, and a central unpaired 
hypopharynx, two mandibles, two maxillce and a lower lip, or labium, 
made up of the fused pair of second maxilla;. These parts may be 
greatly modified, dependent upon whether they are used for biting, 
sucking, piercing and sucking, or a combination of biting and sucking. 

Roughly speaking, insects may be grouped into those which 
undergo complete metamorphosis and those which have incomplete 
metamorphosis. They are said to undergo complete metamorphosis 
when the young form, as it leaves the egg, bears no resemblance to 
the adult. For example, the maggot changes to a quiescent pupa 
and from this emerges the winged active fly. They undergo incom¬ 
plete metamorphosis, when the young insect, as it leaves the egg, 
resembles the adult to a greater or less extent, and after under¬ 
going a certain number of molts becomes sexually mature. 

Representatives of several orders have been reported as accidental 
or faculative parasites of man, but the true parasites are restricted 
to four orders. These are the Siphunculata; the Hemiptera, the 
Diptcra and the Siphonaptera. 

Siphunculata 

The order Siphunculata was established by Mcinert to include the 
true sucking lice. These arc small wingless insects, with reduced 
mouth-parts, adapted for sucking; thorax apparently a single piece 
due to indistinct separation of its three segments; the compound eyes 


Siphunculata, or Lice 


81 


reduced to a single ommatidium on each side. The short, powerful 
legs are terminated by a single long claw. Metamorphosis incom¬ 
plete. 

There has been a great deal of discussion regarding the structure 
of the mouth-parts, and the relationships of the sucking lice, and the 

questions cannot yet be re¬ 
garded as settled. The con¬ 
flicting views are well repre¬ 
sented by Cholodkovsky 
(1904 and 1905) and by 
Enderlein (1904). 

Following Graber, it is 
generally stated that the 
mouth-parts consist of a 
short tube furnished with 
hooks in front, which consti¬ 
tutes the lower lip, and that within this is a delicate sucking tube 
derived from the fusion of the labrum and the mandibles. Opposed 
to this, Cholodkvosky and, more recently, Pawlowsky, (1906), have 
shown that the piercing apparatus lies in a blind sac under the 
pharynx and opening into the mouth cavity (fig. 64). It does not 
form a true tube but a furrow with its open surface uppermost. 
Eysell has shown that, in addition, there is a pair of chitinous rods 
which he regards as the homologues of the maxillae. 

When the louse feeds, it everts the anterior part of the mouth 
cavity, with its circle of hooks. The latter serve for anchoring 
the bug, and the piercing apparatus is then pushed 
out. 

Most writers have classed the sucking lice as a 
sub-order of the Hemiptera, but the more recent 
anatomical and developmental studies render this 
grouping untenable. An important fact, bearing on 
the question, is that, as shown by Gross, (1905), 
the structure of the ovaries is radically different 
from that of the Hemiptera. 

. . . 65. P e d 1 c u 1 u s hu- 

Lice infestation and its effects are known medi- manus, ventral as- 

... pectofmale. (X 10) 

cally as pediculosis. Though their continued pres¬ 
ence is the result of the grossest neglect and filthiness, the original 
infestation may be innocently obtained and by people of the most 
careful habits. 




64. Pediculus showing the blind sac (6) containing the 
mouth parts (a) beneath the alimentary canal 
( p ). After Pawlowsky. 













82 


Parasitic Arthropods 



Three species commonly attack man. Strangely enough, there 
are very few accurate data regarding their life history. 

Pediculus humanus (fig. 65), the head louse, is the most widely 
distributed. It is usually referred to in medical literature as Pedi¬ 
culus capitis, but the Linnean specific name has priority. In color 
it is of a pale gray, blackish on the margins. It is claimed by some 
authors that the color varies according to the color of the skin of the 

host. The abdomen is 


composed of seven dis¬ 
tinct segments, bearing 
spiracles laterally. 
There is considerable 
variation in size. The 
males average 1.8 mm. 
and the females 2.7 mm. 
in length. 

The eggs, fifty to 
sixty in number, stick 
firmly to the hairs of 
the host and are known 
as nits. They are large 
and conspicuous, especi¬ 
ally on dark hair and 
are provided with an 
operculum, or cap, at 
the free end, where the 
nymphs emerge. They 
hatch in about six days 
and about the eigh¬ 
teenth day the young 
lice are sexually mature. 

The head lice live by preference on the scalp of their host but 
occasionally they are found on the eyelashes and beard, or in the 
pubic region. They may also occur elsewhere on the body The 
penetration of the rostrum into the skin and the discharge of an irritat¬ 
ing saliva produce a severe itching, accompanied by the formation 
of an eczema-like eruption (fig. 66). When the infestation is severe, 
the discharge from the pustules mats down the hair, and scabs are 
formed, under which the insects swarm. “ If allowed to run, a regular 
carapace may form, called trichoma, and the head exudes a foetid 


66 . 


Pediculosis of the head. The illustration shows the 
characteristic indications of the presence of lice, viz: 
the occipital eczema gluing the hairs together, the 
swollen cervical glands, and the porrigo, or erup¬ 
tion of contagious pustules upon the neck. After 
Fox. 



Pediculus Humanus 83 

odor. Various low plants may grow in the trichoma, the whole 
being known as -plica palonica.’ ’ — Stiles. 

Sources of infestation are various. School children may obtain 
the lice from seatmates, by wearing the hats or caps of infested mates, 
or by the use, in common, of brushes and combs. They may be 
obtained from infested beds or sleeper berths. Stiles reports an in¬ 
stance in which a large number of girls in a fashionable boarding 
school developed lousiness a short time after traveling in a sleeping 
car. 

Treatment is simple, for the parasites may readily be controlled 
by cleanliness and washing the head with a two per cent solution of 
carbolic acid or even kerosene. The latter is better used mixed with 
equal parts of olive oil, to avoid irritation. The treatment should 
be applied at night and followed the next morning by a shampoo with 
soap and warm water. It is necessary to repeat the operation in a 
few days. Xylol, used pure, or with the addition of five per cent 
of vaseline, is also very efficacious. Of course, the patient must be 
cautioned to stay away from a lighted lamp or fire while using either 
the kerosene or xylol. While these treatments will kill the eggs or 
nits, they will not remove them from the hairs. Pusey recommends 
repeated washings with vinegar or 2 5 per cent of acetic acid in water, 
for the purpose of loosening and removing the nits. 

Treatment of severe infestations in females is often troublesome 
on account of long hair. For such cases the following method recom¬ 
mended by Whitfield (1912) is especially applicable: 

The patient is laid on her back on the bed with her head over the 
edge, and beneath the head is placed a basin on a chair so that the 
hair lies in the basin. A solution of 1 in 40 carbolic acid is then poured 
over the hair into the basin and sluiced backwards and forwards 
until the whole of the hair is thoroughly soaked with it. It is especi¬ 
ally necessary that care should be taken to secure thorough satura¬ 
tion of the hair over the ears and at the nape of the neck, since these 
parts are not only the sites of predilection of the parasites but they 
are apt to escape the solution. This sluicing is carried out for ten 
minutes by the clock. At the end of ten minutes the hair is lifted 
from the basin and allowed to drain, but is not dried or even tho¬ 
roughly wrung out. The whole head is then swathed with a thick 
towel or better, a large piece of common house flannel, which is 
fastened up to form a sort of turban, and is allowed to remain thus 
for an hour. It can then be washed or simply allowed to dry, as the 


84 


Parasitic Arthropods 


carbolic quickly disperses. At the end of this period every pedicu- 
lus and what is better, every ovum is dead and no relapse wall occur 
unless there is exposure to fresh contagion. Whitfield states that 
there seem to be no disadvantages in this method, which he has used 
for years. He has never seen carboluria result from it, but would 
advise first cutting the hair of children under five years of age. 

Pediculus corporis (= P. vestimenti ) the body louse, is larger than 
the preceding species, the female measuring 3.3 mm., and the male 
3 mm. in length. The color is a dirty white, or grayish. P. corporis 
has been regarded by some authorities as merely a variety of P. 
humanus but Piaget maintains there are good characters separating 
the two species. 

The body louse lives in the folds and seams of the clothing of its 
host, passing to the skin only when it wishes to feed. Brumpt 
states that he has found enormous numbers of them in the collars 
of glass-ware or grains worn by certain naked tribes in Africa. 

Exact data regarding the life-history of this species have been 
supplied, in part, by the work of Warburton (1910), cited by Nuttall. 
He found that Pediculus corporis lives longer than P. humanus under 
adverse conditions. This is doubtless due to its living habitually 
on the clothing, whereas humanus lives upon the head, where it has 
more frequent opportunities of feeding. He reared a single female 
upon his own person, keeping the louse enclosed in a cotton-plugged 
tube with a particle of cloth to which it could cling. The tube was 
kept next to his body, thus simulating the natural conditions of 
warmth and moisture under which the lice thrive. The specimen 
was fed twice daily, while it clung to the cloth upon which it rested. 
Under these conditions she lived for one month. Copulation com¬ 
menced five days after the female had hatched and was repeated a 
number of times, sexual union lasting for hours. The female laid 
one hundred and twenty-four eggs within twenty-five days. 

The eggs hatched after eight days, under favorable conditions, 
such as those under which the female was kept. They did not 
hatch in the cold. Eggs kept near the person during the day and 
hung in clothing by the bedside at night, during the winter, in a cold 
room, did not hatch until the thirty-fifth day. When the nymphs 
emerge from the eggs, they feed at once, if given a chance to do so. 
They are prone to scatter about the person and abandon the frag¬ 
ment of cloth to which the adult clings. 


Pediculus Corporis 


85 


The adult stage is reached on the eleventh day, after three molts, 
about four days apart. Adults enter into copulation about the 
fifth day and as the eggs require eight days for development, 
the total cycle, under favorable conditions, is about twenty- 
four days. Warburton’s data differ considerably from those com¬ 
monly quoted and serve to emphasize the necessity for detailed studies 
of some of the commonest of parasitic insects. 

Body lice are voracious feeders, producing by their bites and the 
irritating saliva which they inject, rosy elevations and papules which 
become covered with a brownish 
crust. The intense itching pro¬ 
vokes scratching, and character¬ 
istic white scars (fig. 67) sur¬ 
rounded by brownish pigment 
(fig. 68) are formed. The skin 
may become thickened and take 
on a bronze tinge. This mela¬ 
noderma is especially marked 
in the region between the shoul¬ 
ders but it may become genera¬ 
lized, a prominent characteristic 
of “vagabond’s disease.” Ac¬ 
cording to Dubre and Beille, 
this melanoderma is due to a 
toxic substance secreted by the 
lice, which indirectly provokes 
the formation of pigment. 

Control measures, in the case 
of the body louse, consist in 
boiling or steaming the clothes or in some cases, sterilizing by dry heat. 
The dermatitis may be relieved by the use of zinc-oxide ointment, 
to which Pusey recommends that there be added, on account of their 
parasiticidal properties, sulphur and balsam of Peru, equal parts, 15 
to 30 grains to the ounce. 

Phthirius pubis (= P. inguinalis ), the pubic louse, or so-called 
“crab louse,” differs greatly from the preceding in appearance. It is 
characterized by its relatively short head which fits into a broad 
depression in the thorax. The latter is broad and flat and merges 
into the abdomen. The first pair of legs is slender and terminated 
by a straight claw. The second and third pairs of legs are thicker 



67. Pediculosis in man caused by the body 
louse. After Morrow. 







86 


Parasitic Arthropods 



and are provided with powerful claws fitted for clinging to hairs. 
The females (fig. 69) measure 1.5 to 2 mm. in length by 1.5 mm. in 

breadth. The male averages a 
little over half as large. The eggs, 
or nits, are fixed at the base of the 
hairs. Only a few, ten to fifteen 
are deposited by a single female, 
and they hatch in about a week’s 
time. The young lice mature in 
two weeks. 

The pubic louse usually infests 
the hairs of the pubis and the 
perineal region. It may pass to 
the arm pits or even to the beard 
or moustache. Rarely, it occurs 
on the eyelids, and it has even 
been found, in a very few instances, 
occurring in all stages, on the scalp. 
Infestation may be contracted 
from beds or even from badly in¬ 
fested persons in a crowd. We 
have seen several cases which un¬ 
doubtedly were due to the use of 
public water closets. It produces 
papular eruption and an intense 
pruritis. When abundant, there 
occurs a grayish discoloration of 
the skin which Duguet has shown 
is due to a poisonous saliva injected by the louse, 
as is the melanoderma caused by the body louse. 

The pubic louse may be exterminated by the <5 ~' ~~~ 
measures recommended for the head louse, or / /// 
by the use of officinal mercurial ointment. 


68. Melanoderma caused by the body 
louse. From Portfolio of Dermo- 
chromes. by permission of Rebman 
& Co., New York, Publishers. 


IIemiptera 


Several species of Hemiptera-Heteroptera are 69 Phthirius pubi ,. Ven _ 
habitual parasites of man, and others occur jv'iof pect of ^ emalc - 
as occasional or accidental parasites. Of all 

these, the most important and widespread are the bed-bugs, belong¬ 
ing to the genus Cimex (= Acanthia). 



The Bed-hugs 


87 


The Bed-bugs—The bed-bugs are characterized by a much flat¬ 
tened oval body, with the short, broad head unconstricted behind, 
and fitting into the strongly excavated anterior margin of the thorax. 
The compound eyes are prominent, simple eyes lacking. Antennae 
four-jointed, the first segment short, the second long and thick, and 
the third and fourth slender. The tarsi are short and three seg¬ 
mented. 

It is often assumed in the literature of the subject that there is 
but a single species of Cimex attacking man, but several such species 
are to be recognized. These are distinguishable by the characters 

given in Chapter XII. We shall con¬ 
sider especially Cimex lectularius, the 
most common and widespread species. 

Cimex lectularius (= Acanthia 
lectularia, Clinocoris lectularius), is 
one of the most cosmopolitan of human 
parasites but, like the lice, it has been 
comparatively little studied until 
recent years, when the possibility 
that it may be concerned with the 
transmission of various diseases has 
awakened interest in the details of 
its life-history and habits. 

The adult insect (fig 70) is 4-5 
mm. long by 3 mm. broad, reddish 
brown in color, with the beak and body appendages lighter in color. 
The short, broad and somewhat rectangular head has no neck-like 
constriction but fits into the broadly semilunar prothorax. The 
four segmented labium or proboscis encloses the lancet-like maxillae 
and mandibles. The distal of the four antennal segments is slightly 
club-shaped. The prothorax is characteristic of the species, being 
deeply incised anteriorly and with its thin lateral margins somewhat 
turned up. The mesothorax is triangular, with the apex posteriorly, 
and bears the greatly atrophied first pair of wings. There is no trace 
of the metathoracic pair. The greatly flattened abdomen has eight 
visible segments, though in reality the first is greatly reduced and 
has been disregarded by most writers. The body is densely covered 
with short bristles and hairs, the former being peculiarly saber¬ 
shaped structures sharply toothed at the apex and along the convex 
side (fig. 1596). 



70. Cimex lectularius adult and eggs. 
Photograph by M. V. S. 



88 


Parasitic Arthropods 


The peculiar disagreeable odor of the adult bed-bug is due to the 
secretion of the stink glands which lie on the inner surface of the 
mesostemum and open by a pair of orifices in front of the metacoxae, 
near the middle line. In the nymphs, the thoracic glands are not 
developed but in the abdomen there are to be found three unpaired 
dorsal stink glands, which persist until the fifth molt, when they 
become atrophied and replaced by the thoracic glands. The nymphal 
glands occupy the median dorsal portion of the abdomen, opening 
by paired pores at the anterior margin of the fourth, fifth and sixth 
segments. The secretion is a clear, oily, volatile fluid, strongly acid 
in reaction. Similar glands are to be found in most of the Hemiptera- 
Heteroptera and their secretion is doubtless protective, through 
being disagreeable to the birds. In the bed-bug, as Marlatt points 
out, “it is probably an illustration of a very common phenomenon 
among animals, i. e., the persistence of a characteristic which is no 
longer of any special value to the possessor.’’ In fact, its possession 
is a distinct disadvantage to the bed-bug, as the odor frequently 
reveals the presence of the bugs, before they are seen. 

The eggs of the bed-bug (fig. 70) are pearly white, oval in out¬ 
line, about a millimeter long, and possess a small operculum or cap 
at one end, which is pushed off when the young hatches. They are 
laid intermittently, for a long period, in cracks and crevices of beds 
and furniture, under seams of mattresses, under loose wall paper, 
and similar places of concealment of the adult bugs. Girault (1905) 
observed a well-fed female deposit one hundred and eleven eggs 
during the sixty-one days that she was kept in captivity. She had 
apparently deposited some of her eggs before being captured. 

The eggs hatch in six to ten days, the newly emerged nymphs 
being about 1.5 mm. in length and of a pale yellowish white color. 
They grow slowly, molting five times. At the last molt the mesa- 
thoracic wing pads appear, characteristic of the adult. The total 
length of the nymphal stage varies greatly, depending upon condi¬ 
tions of food supply, temperature and possibly other factors. Mar¬ 
latt (1907) found under most favorable conditions a period averaging 
eight days between molting which, added to an equal egg period, 
gave a total of about seven weeks from egg to adult insect. Girault 
(1912) found the postembryonic period as low as twenty-nine days 
and as high as seventy days under apparently similar and normal 
conditions of food supply. Under optimum and normal conditions 
of food supply, beginning August 27, the average nymphal life was 


The Bed-bugs 


89 


69.9 days; average number of meals 8.75 and the molts 5. Under 
conditions allowing about half the normal food supply the average 
nymphal life was from 116.9 to 139 days. Nymphs starved from 
birth lived up to 42 days. We have kept unfed nymphs, of the first 
stage, alive in a bottle for 75 days. The interesting fact was brought 
out that under these conditions of minimum food supply there were 
sometimes six molts instead of the normal number. 

The adults are remarkable for their longevity, a factor which is 
of importance in considering the spread of the insect and methods of 
control. Dufour (1833) (not De Geer, as often stated) kept speci¬ 
mens for a year, in a closed vial, without food. This ability, coupled 
with their willingness to feed upon mice, bats, and other small mam¬ 
mals, and even upon birds, accounts for the long periods that deserted 
houses and camps may remain infested. There is no evidence that 
under such conditions they are able to subsist on the starch of the 
wall paper, juices of moistened wood, or the moisture in the accumu¬ 
lations of dust, as is often stated. 

There are three or four generations a year, as Girault’s breeding 
experiments have conclusively shown. He found that the bed-bug 
does not hibernate where the conditions are such as to allow it to 
breed and that breeding is continuous unless interrupted by the lack 
of food or, during the winter, by low temperature. 

Bed-bugs ordinarily crawl from their hiding places and attack 
the face and neck or uncovered parts of the legs and arms of their 
victims. If undisturbed, they will feed to repletion. We have 
found that the young nymph would glut itself in about six minutes, 
though some individuals fed continuously for nine minutes, while 
the adult required ten to fifteen minutes for a full meal. When 
gorged, it quickly retreats to a crack or crevice to digest its meal, 
a process which requires two or three days. The effect of the bite 
depends very greatly on the susceptibility of the individual attacked. 
Some persons are so little affected that they may be wholly ignorant 
of the presence of a large number of bugs. Usually the bite produces 
a small hard swelling, or wheal, whitish in color. It may even be 
accompanied by an edema and a disagreeable inflammation, and in 
such susceptible individuals the restlessness and loss of sleep due to 
the presence of the insects may be a matter of considerable im¬ 
portance. Stiles (1907) records the case of a young man who under¬ 
went treatment for neurasthenia, the diagnosis being agreed upon by 
several prominent physicians; all symptoms promptly disappeared, 


go 


Parasitic Arthropods 


however, immediately following a thorough fumigation of his rooms, 
where nearly a pint of bed-bugs were collected. 

It is natural to suppose that an insect which throughout its whole- 
life is in such intimate relationship with man should play an important 
r 61 e in the transmission of disease. Yet comparatively little is-, 
definitely known regarding the importance of the bed-bug in this, 
respect. It has been shown that it is capable of transmitting the 
bubonic plague, and South American trypanosomiasis. Nuttall 
succeeded in transmitting European relapsing fever from mouse to- 
mouse by its bite. It has been claimed that Oriental sore, tubercu¬ 
losis, and even syphilis may be so carried. These phases of the 
subject will be considered later. 

The sources of infestation are many, and the invasion of a house 
is not necessarily due to neglect, though the continued presence of 
the pests is quite another matter. In apartments and closely placed 
houses they are known to invade new quarters by migration. They 
are frequently to be met with in boat and sleeper berths, and even 
the plush seats of day coaches, whence a nucleus may be carried in 
baggage to residences. They may be brought in the laundry or 
in clothes of servants. 

Usually they are a great scourge in frontier settlements and it is. 
generally believed that they live in nature under the bark of trees, 
in lumber, and under similar conditions. This belief is founded upon 
the common occurrence of bugs resembling the bed-bug, in such 
places. As a matter of fact, they are no relation to bed-bugs but 
belong to plant-feeding forms alone (fig. 19 c, d). 

It is also often stated that bed-bugs live in poultry houses, in 
swallows nests, and on bats, and that it is from these sources that they 
gain access to dwellings. These bugs are specifically distinct from 
the true bed-bug, but any of them may, rarely, invade houses. 
Moreover, chicken houses are sometimes thoroughly infested with 
the true Cimex lectularius. 

Control measures consist in the use of iron bedsteads and the 
reduction of hiding places for the bugs. If the infestation is slight 
they may be exterminated by a vigilant and systematic hunt, and 
by squirting gasoline or alcohol into cracks and crevices of the beds, 
and furniture. Fumigation must be resorted to in more general 
infestations. 

The simplest and safest method of fumigation is by the use of 
flowers of sulphur at the rate of two pounds to each one thousand 


The Bed-hugs 


9i 


cubic feet of room space. The sulphur should be placed in a pan, 
a well made in the top of the pile and a little alcohol poured in, to 
facilitate burning. The whole should be placed in a larger pan 
and surrounded by water so as to avoid all danger of fire. Windows 
should be tightly closed, beds, closets and drawers opened, and 
bedding spread out over chairs in order to expose them fully to the 
fumes. As metal is tarnished by the sulphur fumes, ornaments, 
clocks, instruments, and the like should be removed. When all is 
ready the sulphur should be fired, the room tightly closed and left 
for twelve to twenty-four hours. Still more efficient in large houses, 
or where many hiding places favor the bugs, is fumigation with 
hydrocyanic acid gas. This is a deadly poison and must be used 
under rigid precautions. Through the courtesy of Professor Herrick, 
who has had much experience with this method, we give in the Ap¬ 
pendix, the clear and detailed directions taken from his bulletin on 
“Household Insects.” 

Fumigation with formaldehyde gas, either from the liquid or 
“solid” formalin, so efficient in the case of contagious diseases, is 
useless against bed-bugs and most other insects. 

Other Bed-bugs — Cimex hemipterus (= C. rotundatus ) is a trop¬ 
ical and subtropical species, occurring in both the old and new world. 
Patton and Cragg state that it is distributed throughout India, 
Burma, Assam, the Malay Peninsula, Aden, the Island of Mauri¬ 
tius, Reunion, St. Vincent and Porto Rico. “It is wddely distribu¬ 
ted in Africa, and is probably the common species associated there 
with man.” Brumpt also records it for Cuba, the Antilles, Brazil, 
and Venezuela. 

This species, which is sometimes called the Indian bed-bug, 
differs from C. lectularius in being darker and in having a more 
elongate abdomen. The head also is shorter and narrower, and the 
prothorax has rounded borders. 

It has the same habits and practically the same life cycle as 
Cimex lectularius. Mackie, in India, has found that it is capable 
of transmitting the Asiatic type of recurrent fever. Roger suggested 
that it was also capable of transmitting kala-azar and Patton has 
described in detail the developmental stages of Leishmania, the 
causative organism of Kala-azar, in the stomach of this bug, but 
Brumpt declares that the forms described are those of a common, 
non-pathogenic flagellate to be found in the bug, and have nothing 


92 


Parasitic Arthropoda 


to do with the human disease. Brumpt has shown experimentally 
that Cimex hemipterus may transmit Trypanosoma cruzi in its excre¬ 
ment. 

Cimex boueti, occurring in French Guinea, is another species 
attacking man. Its habits and general life history are the same as 
for the above species. It is 3 to 4.5 mm. in length, 
has vestigial elytra, and much elongated antennae and 
legs. The extended hind legs are about as long as the 
body. 

Cimex columbarius, a widely distributed species nor¬ 
mally living in poultry houses and dovecotes, C.inodorus, 
infesting poultry in Mexico, C. hirundinis, occurring in 
the nests of swallows in Europe and Oeciacus vicarius 
(fig. 1 gi) occurring in swallow’s nests in this country, 
sangu°isugus nus are species which occasionally infest houses and attack 
man. 

Conorhinus sanguisugus , the cone-nosed bed-bug. We have seen 
in our consideration of poisonous insects, that various species of 
Reduviid bugs readily attack man. Certain of these are nocturnal 
and are so commonly found in houses that they have gained the 
name, of “big bed-bugs.” The most noted of these, in the United 
States, is Conorhinus sangiusugus (fig. 71), which is widely dis¬ 
tributed in our Southern States. 

Like its near relatives, Conorhinus 
sangiusugus is carnivorous in habit and 
feeds upon insects as well as upon 
mammalian and human blood. It is 
reported as often occurring in poultry 
houses and as attacking horses in 
barns. The life history has been 
worked out in considerable detail by 
Marlatt, (1902), from whose account we 
extract the following. 

The eggs are white, changing to 
yellow and pink before hatching. The 
young hatch within twenty days 
and there arc four nymphal stages. 

In all these stages the insect is active and predaceous, the mouth- 
parts (fig. 72) being powerfully developed. The eggs are normally 
deposited, and the early stages are undoubtedly passed, out of doors, 



72. Beak of Conorhinus sanguisugus. 
After Marlatt. 






Cone-nosed, Bugs 


93 


the food of the immature forms being other insects. Immature 
specimens are rarely found indoors. It winters both in the partly 
grown and adult stage, often under the bark of trees or in any 
similar protection, and only in its nocturnal spring and early 
summer flights does it attack men. Marlatt states that this insect 
seems to be decidedly on the increase in the region which it parti¬ 
cularly infests, — the plains region from Texas northward and west¬ 
ward. In California a closely related species of similar habits is 
known locally as the “monitor bug.” 

The effect of the bite of the giant bed-bug on man is often very 
severe, a poisonous saliva apparently being injected into the wound. 
We have discussed this phase of the subject more fully under the 
head of poisonous insects. 

Conorhinus megistus is a Brazilian species very commonly attack¬ 
ing man, and of special interest since Chagas has shown that it is 
the carrier of a trypanosomiasis of man. Its habits and life history 
have been studied in detail by Neiva, (1910). 

This species is now pre-eminent'ly a household insect, depositing 
its eggs in cracks and crevices in houses, though this is a relatively 
recent adaptation. The nymphs emerge in from twenty to forty 
days, depending upon the temperature. There are five nvmphal 
stages, and as in the case of true bed-bugs, the duration of these is 
very greatly influenced by the availability of food and by tempera¬ 
ture. Neiva reckons the entire life cycle, from egg to egg, as requir¬ 
ing a minimum of three hundred and twenty -four days. 

The nymphs begin to suck blood in three to five days after hatch¬ 
ing. They usually feed at night and m the dark, attacking especially 
the face of sleeping individuals. The bite occasions but little pain. 
The immature insects live in cracks and crevices in houses and 
invade the beds which are in contact with walls, but the adults are 
active flyers and attack people sleeping in hammocks. The males 
as well as the females are blood suckers. 

Like many blood-sucking forms, Conorhinus megistus can endure 
for long periods without food. Neiva received a female specimen 
which had been for fifty-seven days alive in a tightly closed box. 
They rarely feed on two consecutive days, even on small quantities 
of blood, and were never seen to feed on three consecutive days. 

Methods of control consist in screening against the adult bugs, 
and the elimination of crevices and such hiding places of the nymphs. 
Where the infestation is considerable, fumigation with sulphur is 
advisable. 


94 Parasitic Arthropoda 

Parasitic Diptera or Flies 

Of the Diptera or two-winged flies, many species occasionally 
attack man. Of these, a few are outstanding pests, many of them 
may also serve to disseminate disease, a phase of our subject which 
will be considered later. We shall now consider the most important 
of the group from the viewpoint of their direct attacks on man. 

Psychodidae or Moth-Flies 

The Psychodidae or Moth-flies, include a few species which attack 
man, and at least one species, Phlebotomus papatasii, is known 
to transmit the so-called “three-day fever” of man. Another species 
is supposed to be the vector of Peruvian verruga. 

The family is made up of small, sometimes very small, nematocer- 
ous Diptera, which are densely covered with hairs, giving them a 
moth-like appearance. The wings are relatively large, oval or 
lanceolate in shape, and when at rest are held in a sloping manner 
over the abdomen, or are held horizontally in such a way as to give 
the insect a triangular outline. Not only is the moth-like appearance 
characteristic, but the venation of the wings (fig. 163, d) is very peculiar 
and, according to Comstock, presents an extremely generalized form. 
All of the longitudinal veins separate near the base of the wing 
except veins R 2 and R 3 and veins Mi and M 2 . Cross veins are 
wanting in most cases. 

Comparatively little is known regarding the life-history and 
habits of the Psychodidae, but one genus, Phlebotomus, contains 
minute, blood-sucking species, commonly known as sand-flies. The 
family is divided into two subfamilies, the Psychodinae and the 
Phlebotominae. The second of these, the Phlebotominae, is of 
interest to us. 

The Phlebotominae — The Phlebotominae differ from the Psychod¬ 
inae in that the radical sector branches well out into the wing rather 
than at the base of the wing. They are usually less hairy than the 
Psychodinae. The ovipositor is hidden and less strongly chitinized. 
The species attacking man belong to the genus Phlebotomus , small 
forms with relatively large, hairy wings which are held upright, 
and with elongate proboscis. The mandibles and maxillae are ser¬ 
rated and fitted for biting. 

According to Miss Summers (1913) there are twenty-nine known 
species of the genus Phlebotomus, five European, eleven Asiatic, 


Phlebotomus Flies 


95 


seven African and six American. One species only, Phlebotomus 
vexator, has been reported for the United States. This was described 
by Coquillett, (1907), from species taken on Plummer’s Island, Mary¬ 
land. It measures only 1.5 mm. in length. As it is very probable 
that this species is much more widely distributed, and that other 
species of these minute flies will be found to occur in our fauna, we 
quote Coquillett’s description. 

Phlebotomus vexator, Coq.: Yellow, the mesonotum brown, 
hairs chiefly brown; legs in certain lights appear brown, but are 
covered with a white tomentum; wings hyaline, unmarked; the first 
vein (Ri) terminates opposite one-fifth of the length- of the first 
submarginal cell (cell R 2 ); this cell is slightly over twice as long 
as its petiole; terminal, horny portion of male claspers slender, 
bearing many long hairs; the apex terminated by two curved spines 
which are more than one-half as long as the preceding part, and just 
in front of these are two similar spines, while near the middle of the 
length of this portion is a fifth spine similar to the others. Length 
1.5 mm. 

The life-history of the Phlebotomus flies has been best worked out 
for the European Phlebotomus papatasii and we shall briefly sum¬ 
marize the account of Doerr and Russ (1913) based primarily on work 
on this species. The European Phlebotomus flies appear at the 
beginning of the warm season, a few weeks after the cessation of the 
heavy rains and storms of springtime. They gradually become more 
abundant until they reach their first maximum, which in Italy is near 
the end of July (Grassi). They then become scarcer but reach a 
•second maximum in September. At the beginning of winter they 
vanish completely, hibernating individuals not being found. 

After fertilization there is a period of eight to ten days before ovi- 
position. The eggs are then deposited, the majority in a single mass 
covered by a slimy secretion from the sebaceous glands. The larvae 
emerge in fourteen to twenty days. There is uncertainty as to the 
length of larval life, specimens kept in captivity remaining fifty or 
more days without transforming. Growth may be much more rapid 
in nature. The larvae do not live in fluid media but in moist detritus 
in dark places. Marett believes that they live chiefly on the excre¬ 
ment of pill-bugs (Oniscidae) and lizards. Pupation always occurs 
during the night. The remnants of the larval skin remain attached 
to the last two segments of the quiescent pupa and serve to attach 
it to the stone on which it lives. The pupal stage lasts eleven to 
sixteen days, the adult escaping at night. 


q6 


Parasitic Arthropoda 


Only the females suck blood. They attack not only man but all 
warm-blooded animals and, according to recent workers, also cold¬ 
blooded forms, such as frogs, lizards, and larvae. Indeed, Townsend 
(1914) believes that there is an intimate relation between Phlebotomus 
and lizards, or other reptiles the world over. The Phlebotomus 
passes the daylight hours within the darkened recesses of the loose 
stone walls and piles of rock in order to escape wind and strong light. 
Lizards inhabit the same places, and the flies, always ready to suck 
blood in the absence of light and wind, have been found more prone 
to suck reptilian than mammalian blood. 

On hot summer nights, when the wind is not stirring, the Phleboto¬ 
mus flies, or sand-flies, as they are popularly called, invade houses and 
sleeping rooms in swarms and attack the inmates. As soon as light 
begins to break the flies either escape to the breeding places, or cool, 
dark places protected from the wind, or a part of them remain in the 
rooms, hiding behind pictures, under garments, and in similar places. 
Wherever the Phlebotomus flies occur they are an intolerable nui¬ 
sance. On account of their small size they can easily pass through 
the meshes of ordinary screens and mosquito curtains. They attack 
silently and inflict a very painful, stinging bite, followed by itching. 
The ankles, dorsum of the feet, wrists, inner elbow, knee joint and 
similar places are favorite places of attack, possibly on account of 
their more delicate skin. 

Special interest has been attracted to these little pests in recent 
years, since it has been shown that they transmit the European 
“pappatici fever” or “three day fever.” More recently yet, it 
appears that they are the carriers of the virus of the Peruvian “ver¬ 
ruga.” This phase of the subject will be discussed later. 

Control measures have not been worked out. As Newstead says, 
“ I11 consideration of the facts which have so far been brought to light 
regarding the economy of Phlebotomus, it is clearly evident that the 
task of suppressing these insects is an almost insurmountable one. 
Had we to deal with insects as large and as accessible as mosquitoes, 
the adoption of prophylactic measures would be comparatively easy, 
but owing to the extremely minute size and almost flea-like habits of 
the adult insects, and the enormous area over which the breeding- 
places may occur, we are faced with a problem which is most difficult 
of solution.” For these reasons, Newstead considers that the only 
really prophylactic measures which can at present be taken, are those 
which are considered as precautionary against the bites of the insects. 


Culcidce, or Mosquitoes 97 

Of repellents, he cites as one of the best a salve composed of the 
following: 


01 . Anisi . 3 grs. 

01 . Eucalypti . 3 grs. 

01 . Terebenth . 3 grs. 


Unq. Acid Borac. 

Of sprays he recommends as the least objectionable and at the 
same time one of the most effective, formalin. “The dark portions 
and angles of sleeping apartments should be sprayed with a one per 
cent, solution of this substance every day during the season in which 
the flies are prevalent. A fine spraying apparatus is necessary for 
its application and an excessive amount must not be applied. It is 
considered an excellent plan also to spray the mosquito curtains 
regularly every day towards sunset; nets thus treated are claimed to 
repel the attacks of these insects.” This effectiveness of formalin is 
very surprising for, as we have seen, it is almost wholly ineffective 
against bed-bugs, mosquitoes, house flies and other insects, where it 
has been tried. 

A measure which promises to be very effective, where it can be 
adopted, is the use of electric fans so placed as to produce a current 
of air in the direction of the windows of sleeping apartments. On 
account of the inability of the Phlebotomus flies to withstand even 
slight breezes, it seems very probable that they would be unable to 
enter a room so protected. 

Culicidae or Mosquitoes 

From the medical viewpoint, probably the most interesting and 
important of the blood-sucking insects are the mosquitoes. Certainly 
this is true of temperate zones, such as those of the United States. 
The result is that no other group of insects has aroused such wide¬ 
spread interest, or has been subjected to more detailed study than 
have the mosquitoes, since their role as carriers of disease was made 
known. There is an enormous literature dealing with the group, but 
fortunately for the general student, this has been well summarized 
by a number of workers. The most important and helpful of the 
general works are those of Howard (1901), Smith (1904), Blanchard 
(1905), Mitchell (1907), and especially of Howard, Dyar, and Knab, 
whose magnificent monograph is still in course of publication. 





g8 


Parasitic Arthropoda 


Aside from their importance as carriers of disease, mosquitoes are 
notorious as pests of man, and the earlier literature on the group is 
largely devoted to references to their enormous numbers and their 
blood-thirstiness in certain regions. They are to be found in all 
parts of the world, from the equator to the Arctic and Antarctic 
regions. Linnaeus, in the “Flora Lapponica,” according to Howard, 
Dyar and Knab, “dwells at some length upon the great abundance of 
mosquitoes in Lapland and the torments they inflicted upon man and 
beast. He states that he believes that nowhere else on earth are they 
found in such abundance and he compares their numbers to the dust 
of the earth. Even in the open, you cannot draw your breath without 
having your mouth and nostrils filled with them; and ointments of 
tar and cream or of fish grease are scarcely sufficient to protect even 
the case-hardened cuticle of the Laplander from their bite. Even in 
their cabins, the natives cannot take a mouthful of food or lie down 
to sleep unless they are fumigated almost to suffocation.” In some 
parts of the Northwestern and Southwestern United States it is 
necessary to protect horses working in the fields by the use of sheets or 
burlaps, against the ferocious attacks of these insects. It is a sur¬ 
prising fact that even in the dry deserts of the western United States 
they sometimes occur in enormous numbers. 

Until comparatively recent years, but few species of mosquitoes 
were known and most of the statements regarding their life-history 
were based upon the classic work of Reaumur (1738) on the biology 
of the rain barrel mosquito, Culex pipiens. In 1896, Dr. Howard 
refers to twenty-one species in the United States, now over fifty are 
known; Giles, in 1900, gives a total of two hundred and forty-two 
for the world fauna, now over seven hundred species are known. 
We have found eighteen species at Ithaca, N. Y. 

All of the known species of mosquitoes are aquatic in the larval 
stage, but in their life-histories and habits such great differences occur 
that we now know that it is not possible to select any one species as 
typical of the group. For our present purpose we shall first discuss 
the general characteristics and structure of mosquitoes, and shall 
then give the life-history of a common species, following this by a 
brief consideration of some of the more striking departures from what 
have been supposed to be the typical condition. 

The Culicidse are slender, nematocerous I ffptcra with narrow wings, 
antennae plumose in the males, and usually with the proboscis much 
longer than the head, slender, firm and adapted for piercing in the 


Culicidce, or Mosquitoes 


99 


female. The most characteristic feature is that the margins of the 
wings and, in most cases, the wing veins possess a fringe of scale-like 
hairs. These may also cover in part, or entirely, the head, thorax, 
abdomen and legs. The females, only, suck blood. 

On account of the importance of the group in this country and the 
desirability of the student being able to determine material in various 
stages, we show in the accompanying figures the characters most 
used in classification. 

The larvae (fig. 73) are elongate, 
with the head and thorax sharply 
distinct. The larval antennae are 
prominent, consisting of a single 
cylindrical and sometimes curved 
segment. The outer third is often 
narrower and bears at its base a 
fan-shaped tuft of hairs, the ar¬ 
rangement and abundance of which 
is of systematic importance. About 
the mouth are the so-called rotary 
mouth brushes, dense masses of 
long hairs borne by the labrum 
and having the function of sweep¬ 
ing food into the mouth. The 

, , , fatral brush $.(5 

form and arrangement or thoracic, <,/ dm 

abdominal, and anal tufts of hair anal .../fgplf 

vary in different species and present ‘ J ' IL /// DonaJ. tufa 

characteristics of value. On either / 7 I 

side of the eighth abdominal seg- 73 - Ct ^ucture showing details of external 

ment is a patch of scales varying 

greatly in arrangement and number and of much value in separating 
species. Respiration is by means of tracheae which open at the apex 
of the so-called anal siphon, when it is present. In addition, there 
are also one or two pairs of tracheal gills which vary much in appear¬ 
ance in different species. On the ventral side of the anal siphon is a 
double row of flattened, toothed spines whose number and shape are 
likewise of some value in separating species. They constitute the 
comb or pecten. 

The pupa (fig. 139,b) unlike that of most insects, is active, though it 
takes no food. The head and thorax are not distinctly separated, but 
the slender flexible abdomen in sharply marked off. The antennae, 


dnk.il rial 
tuft-, 

1 \ Pltuth brush • 


dnknna 



IOO 


Parasitic Arthropoda 


mouth-parts, legs, and wings of the future adult are now external, but 
enclosed in chitinous cases. On the upper surface, near the base of 
the wings are two trumpets, or breathing tubes, for the pupal spiracles 
are towards the anterior end instead of at the caudal end, as in the 
larva. At the tip of the abdomen is a pair of large chitinous swim¬ 
ming paddles. 

As illustrative of the life cycle of a mosquito we shall discuss the 
development of a common house mosquito, Culex pipiens, often 
referred to in the Northern United States as the rain barrel mosquito. 
Its life cycle is often given as typical for the entire group, but, as we 
have already emphasized, no one species can serve this purpose. 

The adults of Culex pipiens hibernate throughout the winter in 
cellars, buildings, hollow trees, or similar dark shelters. Early in 
the spring they emerge and deposit their eggs in a raft-like mass. 
The number of eggs in a single mass is in the neighborhood of two 
hundred, recorded counts varying considerably. A single female 
may deposit several masses during her life time. The duration of 
the egg stage is dependent upon temperature. In the warm summer 
time the larvae may emerge within a day. The larvae undergo four 
molts and under optimum conditions may transform into pups in 
about a week’s time. Under the same favorable conditions, the pupal 
stage may be completed in a day’s time. The total life cycle of Culex 
pipiens, under optimum conditions, may thus be completed in a week 
to ten days. This period may be considerably extended under less 
favorable conditions of temperature and food supply. 

Culex pipiens breeds continuously throughout the summer, 
developing in rain barrels, horse troughs, tin cans, or indeed, in any 
standing water about houses, which lasts for a week or more. The 
catch basins of sewers furnish an abundant supply of the pests under 
some conditions. Such places, the tin gutters on residences, and all 
possible breeding places must be considered in attempts to extermi¬ 
nate this species. 

Other species of mosquitoes may exhibit radical departures from 
Culex pipiens in life-history and habits. To control them it is essen¬ 
tial that the biological details be thoroughly worked out for, as 
Howard, Dyar, and Knab have emphasized, “much useless labor and 
expense can be avoided by an accurate knowledge of the habits of the 
species.” For a critical discussion of the known facts the reader is 
referred to their monograph. We shall confine ourselves to a few 
illustrations. 



Culicidce, or Mosquitoes 


IOI 


The majority of mosquitoes in temperate climates hibernate in 
the egg stage, hatching in the spring or even mild winter days in water 
from melting snow. It is such single-brooded species which appear in 
astounding numbers in the far North. Similarly, in dry regions the 
eggs may stand thorough dessication, and yet hatch out with great 
promptness when submerged by the rains. “Another provision to 
insure the species against destruction in such a case, exists in the fact 
* * * that not all the eggs hatch, a part of them lying over until 

again submerged by subsequent rains.’’ In temperate North 
America, a few species pass the winter in the larval state. An inter¬ 
esting illustration of this is afforded by Wyeomia smithii, whose 
larvae live in pitcher plants and are to be found on the coldest winter 
days imbedded in the solid ice. Late in the spring, the adults emerge 
and produce several broods during the summer. 

In the United States, one of the most important facts which has 
been brought out by the intensive studies of recent years is that cer¬ 
tain species are migratory and that they can travel long distances and 
become an intolerable pest many miles from their breeding places. 
This was forcibly emphasized in Dr. Smith’s work in New Jersey, 
when he found that migratory mosquitoes, developing in the salt 
marshes along the coast, are the dominant species largely responsible 
for the fame of the New Jersey mosquito. The species concerned are 
Aedes sollicitans, A. cantator and A. tceniorhynchus. Dr. Smith 
decided that the first of these might migrate at least forty miles 
inland. It is obvious that where such species are the dominant pest, 
local control measures are a useless waste of time and money. Such 
migratory habits are rare, however, and it is probable that the 
majority of mosquitoes do not fly any great distance from their 
breeding places. 

While mosquitoes are thought of primarily as a pest of man, there 
are many species which have never been known to feed upon human 
or mammalian blood, no matter how favorable the opportunity. 
According to Howard, Dyar, and Knab, this is true of Culex territans, 
one of the common mosquitoes in the summer months in the Northern 
United States. There are some species, probably many, in which 
the females, like the males, are plant feeders. In experimental work, 
both sexes are often kept alive for long periods by feeding them upon 
ripe banana, dried fig, raisins, and the like, and in spite of sweeping 
assertions that mosquitoes must have a meal of blood in order to 
stimulate the ovaries to development, some of the common blood- 


102 


Parasitic Arthropoda 


sucking species, notably Culex pipiens, have been bred repeatedly 
without opportunity to feed upon blood. 

The effect of the bite varies greatly with different species and 
depends upon the susceptibility of the individual bitten. Some 
persons are driven almost frantic by the attacks of the pests when 
their companions seem almost unconscious of any inconvenience.. 
Usually, irritation and some degree of inflammation appear shortly 
following the bite. Not infrequently a hardened wheal or even a. 
nodule forms, and sometimes scratching leads to secondary infection 
and serious results. 

The source of the poison is usually supposed to be the salivary 
glands of the insect. As we have already pointed out, (p. 34) r 
Macloskie believed that one lobe of the gland, on each side, was; 
specialized for forming the poison, while a radically different view is. 
that of Schaudinn, who believed that the irritation is due to the- 
expelled contents of the oesophageal diverticula, which contain a. 
gas and a peculiar type of fungi or bacteria. In numerous attempts, 
Schaudinn was unable to produce any irritation by applying the 
triturated salivary glands to a wound, but obtained the typical result, 
when he used the isolated diverticula. 

The irritation of the bite may be relieved to some extent by using 
ammonia water, a one per cent, alcoholic solution of menthol, or 
preparations of cresol, or carbolic acid. Dr. Howard recommends 
rubbing the bite gently with a piece of moist toilet soap. Castellani 
and Chalmers recommend cleansing inflamed bites with one in forty 
carbolic lotion, followed by dressing with boracic ointment. Of 
course, scratching should be avoided as much as possible. 

Repellents of various kinds are used, for warding off the attacks 
of the insects. We have often used a mixture of equal parts of oil 
of pennyroyal and kerosene, applied to the hands and face. Oil of 
citronella is much used and is less objectionable to some persons. A 
recommended formula is, oil of citronella one ounce, spirits of camphor 
one ounce, oil of cedar one-half ounce. A last resort would seem to- 
be the following mixture recommended by Howard, Dyar, and Knab 
for use by hunters and fishermen in badly infested regions, against 
mosquitoes and blackflies. 

Take 2]/^ lbs. of mutton tallow and strain it. While still hot add 
]/2 lb. black tar (Canadian tar). Stir thoroughly and pour into the- 
receptacle in which it is to be contained. When nearly cool stir in 
three ounces of oil of citronella and 1)4 oz. of pennyroyal. 


Culicidce , or Mosquitoes 


103 


At night the surest protection is a good bed net. There are many 
types of these in use, but in order to be serviceable and at the same 
time comfortable it should be roomy and hung in such a way as to 
be stretched tightly in every direction. We prefer one suspended 
from a broad, square frame, supported by a right-angled standard 
which is fastened to the head of the bed. It must be absolutely free 
from rents or holes and tucked in securely under the mattress or it 
will serve merely as a convenient cage to retain mosquitoes which gain 
an entrance. While such nets are a convenience in any mosquito 
riden community, they are essential in regions where disease-carrying 
species abound. Screening of doors, windows and porches, against 
the pests is so commonly practiced in this country that its importance 
and convenience need hardly be urged. 

Destruction of mosquitoes and prevention of breeding are of 
fundamental importance. Such measures demand first, as we have 
seen, the correct determination of the species which is to be dealt 
with, and a knowledge of its life-history and habits. If it prove to be 
one of the migratory forms, it is beyond mere local effort and becomes 
a problem demanding careful organization and state control. An 
excellent illustration of the importance and effectiveness of work 
along these lines is afforded by that in New Jersey, begun by the late 
Dr. John B. Smith and being pushed with vigor by his successor, 
Dr. Headlee. 

In any case, there is necessity for community action. Even near 
the coast, where the migratory species are dominant, there are the 
local species which demand attention and which cannot be reached 
by any measures directed against the species of the salt marshes. The 
most important of local measures consist in the destruction of breed¬ 
ing places by filling or draining ponds and pools, clearing up of more 
temporary breeding places, such as cans, pails, water barrels and the 
like. Under conditions where complete drainage of swamps is im¬ 
practicable or undesirable, judicious dredging may result in a pool or 
series of steep-sided pools deep enough to maintain a supply of fish, 
which will keep down the mosquito larvae. Where water receptacles 
are needed for storage of rain water, they should be protected by 
careful screening or a film of kerosene over the top of the water, 
renewed every two weeks or so, so as to prevent mosquitoes from 
depositing their eggs. When kerosene is used, water drawn from the 
bottom of the receptacle will not be contaminated by it to any in¬ 
jurious extent. Where ponds cannot be drained much good will be 


104 


Parasitic Arthropoda 


accomplished by spraying kerosene oil on the surface of the water, or 
by the introduction of fish which will feed on the larvas. 

Detailed consideration of the 
most efficient measures for con¬ 
trolling mosquitoes is to be found 
in Dr. Howard’s Bulletin No. 88 
of the Bureau of Entomology, 
“Preventive and remedial work 
against mosquitoes” or, in more 
summarized form, in Farmers’ 
Bulletin No. 444. One of these 
should be obtained by any person 
interested in the problems of mos¬ 
quito control and public health. 

The Simuliidae, or Black Flies 

The Simuliidae, or black flies, are small, dark, or black flies, with 
a stout body and a hump-back appearance. The 
antennae are short but eleven-segmented, the wings 
broad, without scales or hairs, and with the anterior 
veins stout but the others very weak. The mouth- 
parts (fig. 74) are fitted for biting. 

The larvae of the Simuliidae (fig. 75) are aquatic 
and, unlike those of mosquitoes, require a well aerated, 
or swiftly running water. Here they attach to stones, 
logs, or vegetation and feed upon various micro¬ 
organisms. They pupate in silken cocoons open at 
the top. Detailed life-histories have not been worked 
out for most of the species. We shall consider as 
typical that of Simulium pictipes, an inoffensive 
species widely distributed in the Eastern United 
States, which has been studied especially at Ithaca, 

N.Y. (Johannsen, 1903). 

The eggs are deposited in a compact yellowish layer 
on the surface of rock, on the brinks of falls and 
rapids where the water is flowing swiftly. They are 75 Larva of Simu _ 
elongate ellipsoidal in shape, about .4 by .18 mm. AfteH^'rmam 
As myriads of females deposit in the same place the 
egg patches may be conspicuous coatings of a foot or much more 
in diameter. When first laid they are enveloped in a yellowish 




74. Mouth parts of Simulium. After 
Grunberg. 





Simuliidce, or Black Flies 


105 

white slime, which becomes darker, until finally it becomes black just 
before the emerging of the larvae. The egg stage lasts a week. 

The larvae (fig. 75) arc black, soft skinned, somewhat cylindrical 
in shape, enlarged at both ends and attenuated in the middle. The 
posterior half is much stouter than the anterior part and almost club- 
shaped. The head bears two large fan-shaped organs which aid in 
procuring food. Respiration is accomplished by means of three so- 
called blood gills which are pushed out from the dorsal part of the 
rectum. The larvae occur in enormous numbers, in moss-like patches. 
If removed from their natural habitat and placed in quiet water they 
die within three or four hours. Fastened to the rock by means of a 
disk-like sucker at the caudal end of 
the body, they ordinarily assume an 
erect position. They move about on 
the surface of the rocks, to a limited 
extent, with a looping gait similar to 
that of a measuring worm, and a web 
is secreted which prevents their being 
washed away by the swiftly flowing 
water. They feed chiefly upon algas 
and diatoms. 

The complete larval stage during 
the summer months occupies about 
four weeks, varying somewhat with the 
temperature and velocity of the water. 

At the end of this period they spin 76 - simuiium venustum, (x8). 

L j 1 After Garman. 

from cephalic glands, boot-shaped 

silken cocoons within which the} 7 pupate. The cocoon when spun 
is firmly attached to the rock and also to adjacent cocoons. 
Clustered continuously over a large area and sometimes one above 
another, they form a compact, carpet-like covering on the rocks, 
the reddish-brown color of which is easily distinguishable from the 
jet-black appearance of the larvae. The pupal stage lasts about 
three weeks. The adult fly, surrounded by a bubble of air, quickly 
rises to the surface'of the water and escapes. The adults (fig. 76) 
are apparently short lived and thus the entire life cycle, from egg 
to egg is completed in approximately eight weeks. 

In the case of Simuiium pictipes at Ithaca, N. Y., the first brood 
of adults emerges early in May and successive generations are produced 
throughout the summer and early autumn. This species winters in 





io6 


Parasitic Arthropoda 


the larval condition. Most of the other species of Simulium which 
have been studied seem to be single brooded. 

While Simulium pictipes does not attack man, there are a number 
of the species which are blood-sucking and in some regions they are a 
veritable scourge. In recent years the greatest interest in the group 
has been aroused by Sambon’s hypothesis that they transmit pellagra 
from man to man. This has not been established, and, indeed, seems 
very doubtful, but the importance of these insects as pests and the 
possibility that they may carry disease make it urgent that detailed 
life-histories of the hominoxious species be worked out. 

As pests a vivid account of their attacks is in Agassiz’s “Lake 
Superior’’ (p. 61), quoted by Forbes (1912). 

“Neither the love of the picturesque, however, nor the interests of 
science, could tempt us into the woods, so terrible were the black flies. 
This pest of flies which all the way hither had confined our ramblings 
on shore pretty closely to the rocks and the beach, and had been 
growing constantly worse, here reached its climax. Although de¬ 
tained nearly two days, * * * we could only sit with folded 

hands, or employ ourselves in arranging specimens, and such other 
operations as could be pursued in camp, and under the protection of 
a ‘smudge.’ One, whom scientific ardor tempted a little way up the 
river in a canoe, after water plants, came back a frightful spectacle, 
with blood-red rings round his eyes, his face bloody, and covered with 
punctures. The next morning his head and neck were swollen as if 
from an attack of erysipelas.” 

There are even well authenticated accounts on record of death of 
humans from the attacks of large swarms of these gnats. In some 
regions, and especially in the Mississippi Valley in this country, cer¬ 
tain species of black flies have been the cause of enormous losses to 
farmers and stockmen, through their attacks on poultry and domestic 
animals. C. V. Riley states that in 1874 the loss occasioned in one 
county in Tennessee was estimated at $500,000. 

The measures of prevention and protection against these insects 
have been well summarized by Forbes (1912). They arc of two kinds: 
“the use of repellents intended to drive away the winged flies, and 
measures for the local destruction of the aquatic larvae. The repel¬ 
lents used arc either smudges, or surface applications made to keep 
the flies from biting. The black-fly will not endure a dense smoke, 
and the well-known mosquito smudge seems to be ordinarily sufficient 
for the protection of man. In the South, leather, cloth, and other 


Simuliidce, or Black Flies 


107 


materials which will make the densest and most stifling smoke, are 
often preserved for this use in the spring. Smudges are built in 
pastures for the protection of stock, and are kept burning before the 
doors of bams and stables. As the black-flies do not readily enter a 
dark room, light is excluded from stables as much as possible during 
the gnat season. If teams must be used in the open field while gnats 
are abroad, they may be protected against the attacks of the gnats by 
applying cotton-seed oil or axle grease to the surface, especially to the 
less hairy parts of the animals, at least twice a day. A mixture of oil 
and tar and, indeed, several other preventives, are of practical use in 
badly infested regions; but no definite test or exact comparison has 
been made with any of them in a way to give a record of the precise 
results.” 

‘‘It is easy to drive the flies from houses or tents by burning 
pyrethrum powder inside; this either kills the flies or stupifies them 
so that they do not bite for some time thereafter.” * * * ‘‘Oil of 

tar is commonly applied to the exposed parts of the body for the pur¬ 
pose of repelling the insects, and this preparation is supplied by the 
Hudson Bay Company to its employees. Minnesota fishermen 
frequently grease their faces and hands with a mixture of kerosene 
and mutton tallow for the same purpose.” We have found a mixture 
of equal parts of kerosene and oil of pennyroyal efficient. 

Under most circumstances very little can be done to destroy this 
insect in its early stage, but occasionally conditions are such that a 
larvicide can be used effectively. Weed (1904), and Sanderson (1910) 
both report excellent results from the use of phinotas oil, a proprietary 
compound. The first-mentioned also found that in some places the 
larvae could be removed by sweeping them loose in masses with stiff 
stable brooms and then catching them downstream on wire netting 
stretched in the water. 

Chironomidse or Midges 

The flies of this family, commonly known as midges, resemble 
mosquitoes in form and size but are usually more delicate, and the 
wing-veins, though sometimes hairy, are not fringed with scales. 
The venation is simpler than in the mosquitoes and the veins are 
usually less distinct. 

These midges, especially in spring or autumn, are often seen in 
immense swarms arising like smoke over swamps and producing a 
humming noise which can be heard for a considerable distance. At 


io8 


Parasitic Arthropoda 


these seasons they are frequently to be found upon the windows of 
dwellings, where they are often mistaken for mosquitoes. 

The larvae are worm-like, but vary somewhat in form in the differ¬ 
ent genera. Most of them are aquatic, but a few live in the earth, in 
manure, decaying wood, under bark, or in the sap of trees, especially 
in the sap which collects in wounds. 

Of the many species of Chironomidae, (over eight hundred known), 
the vast majority are inoffensive. The sub-family Ceratopogoninae, 
however, forms an exception, for some of the members of this group, 



77 . Culicoides guttipennis; (a) adult, (x 15); (6) head of same; (e) larva; 

C d ) head; (e) pupa. After Pratt. 


known as sandflies, or punkies, suck blood and are particularly trouble¬ 
some in the mountains, along streams, and at the seashore. Most of 
these have been classed under the genus Ceratopogon, but the group 
has been broken up into a number of genera and Ceratopogon, in the 
strict sense, is not known to contain any species which sucks the blood 
of vertebrates. 

[* The Ceratopogoninae — The Ceratopogoninae are among the smallest 
of the Diptera, many of them being hardly a millimeter long and some 
not even so large. They are Chironomidae in which the thorax is not 
prolonged over the head. The antennae are filiform with fourteen 
(rarely thirteen) segments in both sexes, those of the male being brush¬ 
like. The basal segment is enlarged, the last segment never longer 





Chironomidce, or Midges 


109 

than the two preceding combined, while the last five are sub-equal to, 
or longer than the preceding segment. The legs are relatively stouter 
than in the other Chironomidae. The following three genera of this 
subfamily are best known as blood suckers in this country. 

Of the genus Culicoides there are many species occurring in various 
parts of the world. A number are known to bite man and animals and 
it is probable that all are capable of inflicting injury. In some 
localities they are called punkies, in others, sand-flies, a name some¬ 
times also applied to the species of Simulium and Phlebotomus. 
Owing to their very small size they are known by some tribes of 
Indians as No-see-ums. The larva? are found in ponds, pools, water 
standing in hollow tree stumps, and the like. Though probably living 
chiefly in fresh water, we have found a species occurring in salt water. 
The larvae are small, slender, legless, 
worm-like creatures (fig. 77 c) with 
small brown head and twelve body 
segments. The pupae (fig. 77c) are 
slender, more swollen at the anterior 
end and terminating in a forked pro¬ 
cess. They float nearly motionless in 
a vertical position, the respiratory 
tubes in contact with the surface film. 

The adults are all small, rarely exceed¬ 
ing 2>4 mm. in length. The wings 
are more or less covered with erect 
setulas or hairs and in many species 
variously spotted and marked with 
iridescent blotches. The antennae have fourteen segments, the palpi 
usually five. The wing venation and mouth-parts are shown in 
figures 77 and 78. Of the twenty or more species of this genus 
occurring in the United States the following are known to bite: C. 
cinctus, C. guttipennis, C. sanguisuga, C. stellifer, C. variipennis, 
C. unicolor. 

One of the most widely distributed and commonest species in the 
Eastern States is C. guttipennis (fig. 77a). It is black with brown 
legs, a whitish ring before the apex of each femur and both ends of 
each tibia; tarsi yellow, knobs of halteres yellow. Mesonotum 
opaque, brown, two vittae in the middle, enlarging into a large spot 
on the posterior half, also a curved row of three spots in front of each 
wing, and the narrow lateral margins, light gray pruinose. Wings 



78. Culicoides guttipennis; mouth 
parts of adult. After Pratt. 










I IO 


Parasitic Arthropoda 


nearly wholly covered with brown hairs, gray, with markings as 
shown in the figure. Length one mm. 

Johannseniella Will, is a 
wide-spread genus related 
to the foregoing. Its 
mouth-parts are well 
adapted for piercing and 
it is said to be a persistent 
blood sucker, particularly 
in Greenland. This genus 
is distinguished from Culi- 
coides by its bare wings, 
the venation (fig. 163,0), 
and the longer tarsal claws. 
There are over twenty 
North American species. 

In the Southwestern United States, Tersesthes torrens Towns, 
occurs, a little gnat which annoys horses, and perhaps man also, by 
its bite. It is related to Culicoides but differs in the number of 
antennal segments and in its wing venation (fig. i63,e). The fly 
measures but two mm. in length and is blackish in color. The 
antennae of the female have thirteen segments, the palpi but three, of 
which the second is enlarged and swollen. 



Tabanidae or Horse-Flies 

The Tabanidae, horse-flies, ear-flies, and deer-flies, — are well- 
known pests of cattle and horses and are often extremely annoying 
to man. The characteristics of the family and of the principal North 
American genera are given in the keys of Chapter XII. There are 
•over 2500 recorded species. As in the mosquitoes, the females 
alone are blood suckers. The males are flower feeders or live on 
plant juices. This is apparently true also of the females of some of 
the genera. 

The eggs are deposited in masses on water plants or grasses and 
sedges growing in marshy or wet ground. Those of a common 
species of Tabanus are illustrated in figure 80, a. They are placed 
in masses of several hundred, light colored when first deposited but 
turning black. In a week or so the cylindrical larvae, tapering at 
both ends (fig. 80, b ), escape to the water, or damp earth, and lead 





Tabanidce, or Horse-flies 


hi 


an active, carnivorous life, feeding mainly on insect larvae, and worms. 
In the forms which have been best studied the larval life is a long 

one, lasting for months or even for more 
than a year. Until recently, little was 
known concerning the life-histories of this 
group, but the studies of Hart (1895), 
and Hine (1903 
+ ) have added 
greatly to the 
knowledge con¬ 
cerning North 
American 
forms. 

Many of the 
species attack 
man with avid¬ 
ity and are able 
to inflict painful 
bites, which 
may smart for 
hours. In some 
instances the 
wound is so 
considerable 
that blood will 
continue to flow 
after the fly has 
left. We have 
seen several 

cases of secondary infection following 
such bites. 

The horse-flies have been definitely 
convicted of transferring the trypanosome 
of surra from diseased to healthy animals 
and there is good evidence that they transfer anthrax. The possi¬ 
bility of their being important agents in the conveyal of human 
diseases should not be overlooked. Indeed, Leiper has recently 
determined that a species of Chrysops transfers the blood parasite 
Filaria diurna. 



80. (6) Larva of Tabanus. 

Photograph by M. V. S. 



80. (a) Eggs of Tabanus. Photo¬ 

graph by J. T. Lloyd. 






11 2 


Leptidce, or Snipe-flies 

Leptidae or Snipe-Flies 

The family Leptidae is made up of moderate or large sized flies, 
predaceous in habit. They are sufficiently characterized in the keys 

of Chapter XII. Four blood¬ 
sucking species belonging to three 
genera have been reported. Of 
these Symphoromyia pachyceras is 
a western species. Dr. J. C. 
Bradley, from personal experience, 
reports it as a vicious biter. 

Oestridae or Bot-flies 

To the family Oestridae belong 
the bot and warble-flies so fre¬ 
quently injurious to animals. 
The adults are large, or of 
medium size, heavy bodied, rather 
hairy, and usually resemble bees in appearance. 

The larvae live parasitieally in various parts of the body of mam¬ 
mals, such as the stomach (horse bot-fly), the subcutaneous con¬ 
nective tissue (warble-fly of cattle), or the nasal passage (sheep bot¬ 
fly or head maggot). 

There are on record many cases of the occurrence of the larvae 
of Oestridae as occasional parasites of man. A number of these have 
been collected and reviewed in a thesis by Mme. Petrovskaia (1910). 
The majority of them relate to the following species. 

Gasirophilus hcemorrhoidalis , the red tailed bot-fly, is one of the 
species whose larvae are most commonly found in the stomach of the 
horse. Schoch (1877) cites the case of a woman who suffered from 
a severe case of chronic catarrh of the stomach, and who vomited, 
and also passed from the anus, larvae which apparently belonged 
to this species. vSuch cases are exceedingly rare but instances of 
subcutaneous infestation are fairly numerous. In the latter type 
these larvae are sometimes the cause of the peculiar “ creeping myasis. 
This is characterized at its beginning by a very painful swelling 
which gradually migrates, producing a narrow raised line four to 
twenty-five millimeters broad. When the larva is mature, sometimes 
after several months, it becomes stationary and a tumor is formed 
which opens and discharges the larva along with pus and scrum. 



80. ( c ) Mouth parts of Tabanus. After Gnin- 

berg. 






Oestridce, or Bot-flies 


113 

Gastrophilus equi is the most widespread and common of the horse 
bot-flies. Portschinsky reports it as commonly causing subcutan¬ 
eous myasis of man in Russia. 

Hypoderma bovis ( = Oestrus bovis), and Hypoderma lineata are 
the so-called warble-flies of cattle. The latter species is the more 
common in North America but Dr. C. G. Hewitt has recently shown 
that H. bovis also occurs. Though warbles are very common in 
cattle in this country, the adult flies are very rarely seen. They 
are about half an inch in length, very hairy, dark, and closely resemble 
common honey-bees. 

They deposit their eggs on the hairs of cattle and the animals in 
licking themselves take in the young larvae. These pass out through 
the walls of the oesophagus and migrate through the tissues of the 
animal, to finally settle down in the subcutaneous tissue of the back. 
The possibility of their entering directly through the skin, especially 
in case of infestation of man, is not absolutely precluded, although 
it is doubtful. 

For both species of Hypoderma there are numerous cases on 
record of their occurrence in man. Hamilton (1893) saw a boy, 
six years of age, who had been suffering for some months from the 
glands on one side of his neck being swollen and from a fetid ulcera¬ 
tion around the back teeth of the lower jaw of the same side. Three 
months’ treatment was of no avail and the end seemed near; one day 
a white object, which was seen to move, was observed in the ulcer 
at the root of the tongue, and on being extracted was recognized as a 
full grown larva of Hypoderma. It was of usual tawny color, about 
half an inch long when contracted, about one third that thickness, 
and quite lively. The case resulted fatally. The boy had been on a 
dairy farm the previous fall, where probably the egg (or larva) was 
in some way taken into his mouth, and the larva found between the 
base of the tongue and the jaw suitable tissue in which to develop. 

Topsent (1901) reports a case of “creeping myasis” caused by 
H. lineata in the skin of the neck and shoulders of a girl eight years 
of age. The larva travelled a distance of nearly six and a half inches. 
The little patient suffered excruciating pain in the place occupied by 
the larva. 

Hypoderma diana infests deer, and has been known to occur in 
man. 

Oestris ovis, the sheep bot-fly, or head maggot, is widely distrib¬ 
uted in all parts of the world. In mid-summer the flies deposit 


Parasitic Arthropoda 


114 

living maggots in the nostrils of sheep. These larvse promptly pass 
up the nasal passages into the frontal and maxi liars 7 sinuses, where 
they feed on the mucous to be found there. In their migrations 
they cause great irritation to their host, and when present in numbers 
may cause vertigo, paroxysms, and even death. Portschinsky in an 
important monograph on this species, has discussed in detail its 
relation to man. He shows that it is not uncommon for the fly to 
attack man and that the minute living larvse are deposited in the 
eyes, nostrils, lips, or mouth. A typical case in which the larvae 
w T ere deposited in the eye was described by a German oculist Kayser, 
in 1905. A woman brought her six year old daughter to him and 
said that the day before, about noontime, a flying insect struck the 
eye of the child and that since then she had felt a pain which in¬ 
creased towards evening. In the morning the pain ceased but the 
eye was very red. She was examined at about noon, at which time 
she was quiet and felt no pain. She was not sensitive to light, and 
the only thing noticed was a slight congestion and accumulation of 
secretion in the comer of the right eye. A careful examination of 
the eye disclosed small, active, white larvae that crawled out from 
the folds of the conjunctiva and then back and disappeared. Five 
of these larvae were removed and although an uncomfortable feeling 
persisted for a while, the eye became normal in about three weeks. 

Some of the other recorded cases have not resulted so favorably, 
for the eyesight has been seriously affected or even lost. 

According to Edmund and Etienne Sergent (1907), myasis caused 
by the larvae of Oestris ovis is very common among the shepherds in 
Algeria. The natives say that the fly deposits its larvae quickly, 
while on the wing, without pause. The greatest pain is caused when 
these larvae establish themselves in the nasal cavities. They then 
produce severe frontal headaches, making sleep impossible. This 
is accompanied by continuous secretion from the nasal cavities 
and itching pains in the sinuses. If the larvae happen to get into 
the mouth, the throat becomes inflamed, swallowing is painful, 
and sometimes vomiting results. The diseased condition may last 
for from three to ten days or in the case of nasal infection, longer, 
but recovery' always follows. The natives remove the larvae from 
the eye mechanically by means of a small rag. When the nose is 
infested, tobacco fumigations are applied, and in case of throat 
infestation gargles of pepper, onion, or garlic extracts are used. 


Oestrides, or Bot-flies 


US 


Rhincestrus nasalis, the Russian gad-fly, parasitizes the naso¬ 
pharyngeal region of the horse. According to Portschinsky, it not 

infrequently attacks man 
and then, in all the known 
cases deposits its larvae 
in the eye, only. This 
is generally done while 
the person is quiet, but 
not during sleep. The 
fly strikes without stop¬ 
ping and deposits its larva 
instantaneously. Imme¬ 
diately after, the victim 
experiences lancinating 
pains which without in¬ 
termission increase in 
violence. There is an in¬ 
tense conjunctivitis and 




81. 


Larvae of Dermatobia cyaniventris. 

chard. 


After Blan- 


if the larvae are not removed promptly the envelopes 
ot the eye are gradually destroyed and the organ 
lost. 

Dermatobia cyaniventris —This fly (fig. 83) is widely 
■distributed throughout tropical America, and in its 
larval stage is well known as a parasite of man. The 
larvae (figs. 81 and 82) which are known as the “ver 
macaque,” “torcel,” “ver moyocuil” or by several other 
local names, enter the skin and give rise to a boil-like 
swelling, open at the top, and comparable with the swell¬ 
ing produced by the warble fly larvae, in cattle. They 
cause itching and occasional excruciating pain. When 
mature, nearly an inch in length, they voluntarily 
leave their host, drop to the ground and complete their 
development. The adult female is about 12 mm. in 
length. The face is yellow, the frons black with a 
grayish bloom; antennae yellow, the third segment 
four times as long as the second, the arista pectinate. 
The thorax is bluish black with grayish bloom; the 
abdomen depressed, brilliant metallescent blue with 
violet tinge. The legs are yellowish, the squamae and 
wings brownish. 


82. Young larva of 
Dermatobia cy¬ 
aniventris. 

After Surcouf. 









n6 Parasitic Arthropoda 

The different types of larvae represented in figure Si were formerly 
supposed to belong to different species but Blanchard regards them 

as merely various stages 
of the same species. It 
is only very recently 
that the early stage and 
the method by which 
man becomes infested 
were made known. 

About 1900, Blanch¬ 
ard observed the pres¬ 
ence of packets of large¬ 
sized eggs under the 
abdomen of certain mos- 

83. Dermatobia cyaniventris (xlj<). After Graham-Smith. qUltoeS from Central 

America; and in 1910, 
Dr. Morales, of Costa Rica, declared that the Dermatobia deposited 
its eggs directly under the abdomen of the mosquito and that they 
were thus carried to vertebrates. 

Dr. Nunez Tovar observed the 
mosquito carriers of the eggs and 
placing larvae from this source on 
animals, produced typical tumors 
and reared the adult flies. It 
remained for Sureouf (1913) to 
work out the full details. He 
found that the Dermatobia de¬ 
posits its eggs in packets covered 
by a very viscid substance, on 
leaves. These become attached 
to mosquitoes of the species 
Janthinosoma lutzi (fig. 84) which 
walk over the leaves. The eggs 
which adhere to the abdomen, 
remain attached and are thus 
transported. The embryo de¬ 
velops, but the young larva (fig. 82) remains in the egg until it has 
opportunity to drop upon a vertebrate fed upon by the mosquito. 



84. Mosquito carrying eggs of Dermatobia 
cyaniventris. After Sureouf. 














The Muscidce 


117 


Muscidae 



The following Muscidae, characterized elsewhere, deserve special 
mention under our present grouping of parasitic species. Other 
important species will be considered as facultative para¬ 
sites. 

Stomoxys calcitrans, the stable-fly, or the biting house¬ 
fly, is often confused with Musca domestica and therefore 
is discussed especially in our consideration of the latter 
species as an accidental carrier of disease. Its possible 
relation to the spread of infantile paralysis is also con¬ 
sidered later. 

The tsetse flies, belonging to the genus Glossina, are 
African species of blood-sucking Muscidae which have 
attracted much attention because of their role in trans- 
8.5 L arva of mitting various trypanosome diseases of man and animals. 
oil' 13 ' After They are characterized in Chapter XII and are also 
Smith am ’ di scusse d in connection with the diseases which they 
convey. 

Chrysomyia macellaria, (= Compsomyia ), the “screw worm”-fly 
is one of the most important species of flies directly affecting man, 
in North America. It is not normally parasitic, however, and hence 
will be considered witlC other facultative parasites in Chapter IV. 

Auchmeromyia lute- 
ola, the Congo floor 
maggot. This is a 
muscid of grewsome 
habits, which has a wide 
distribution throughout 
Africa. The fly (fig. 86) 
deposits its eggs on the 
ground of the huts of the 
natives. The whitish 
larvae (fig. 85) on hatch¬ 
ing are slightly flat¬ 
tened ventrally, and 
each segment bears 
posteriorly three foot¬ 
pads transversely arranged. At night the larvae find their way into the 
low beds or couches of the natives and suck their blood. The adult 
flies do not bite man and, as far as known, the larvae do not play any 
role in the transmission of sleeping sickness or other diseases. 



86. Auchmeromyia luteola (X4). After Graham-Smith. 









118 


Parasitic Arthropoda 



87. Cordylobia anthropophaga (x3). 
After Fulleborn. 


This habit of blood-sucking by museid larvae is usually referred 
to as peculiar to Aucheromyia luteola but it should be noted that the 

larvae of Protocalliphora frequent the 
nests of birds and feed upon the 
young. Mr. A. F. Coutant has studied 
especially the life-history and habits 
of P. azurea, whose larvae he found 
attacking young crows at Ithaca, N.Y. 
He was unable to induce the larvae to 
feed on man. 

Cordylobia anthropophaga, ( Ochro - 
myia anthropophaga), or Tumbu-fly 
(fig. 87) is an African species whose 
larva; affect man much as do those of 
Dermatobia cyniventris, of Central and 
South America. The larva (fig. 88), which is known as “ver du 
Cayor” because it was first observed in Cayor, in Senegambia, 
develops in the skin of man and of various animals, such as dogs, 
cats, and monkeys. It is about 12 mm. in length, and of the form 
of the larvae of other muscids. Upon the intermediate segments are 
minute, brownish recurved spines which give to the larva its char¬ 
acteristic appearance. The life-history is not satisfactorily worked 
out, but Fuller (1914), after reviewing 
the evidence believes that, as a rule, it 
deposits its young in the sleeping places 
of man and animals, whether such be a 
bed, a board, the floor, or the bare ground. 

In the case of babies, the maggots may 
be deposited on the scalp. The minute 
maggots bore their way painlessly into 
the skin. As many as forty parasites 
have been found in one individual and 
one author has reported finding more 
than three hundred in a spaniel puppy. 

Though their attacks are at times ex¬ 
tremely painful, it is seldom that any 
serious results follow. 














The Siphonaptera or Fleas 119 

The Siphonaptera or Fleas 

The Siphonaptera, or fleas (fig. 89) are wingless insects, with 
highly chitinized and laterally compressed bodies. The mouth-parts 
are formed for piercing and sucking. Compound eyes are lacking 
but some species possess ocelli. The metamorphosis is complete. 

This group of parasites, concerning which little was known until 
recently, has assumed a very great importance since it was learned 



that fleas are the carriers of bubonic plague. Now over four hundred 
species are known. Of these, several species commonly attack man. 
The most common hominoxious species are Pulex irritans, Xenopsylla 
cheopis, Ctenocephalus cams, Ctenocephalus jelis, Ceratophyllus 
fasciatus and Dermatophilus penetrans, but many others will feed 
readily on human blood if occasion arises. 

We shall treat in this place of the general biology and habits of 
the hominoxious forms and reserve for the systematic section the 
discussion of the characteristics of the different genera. 





120 


Parasitic Arthropoda 



Dog flea (xl5). After Howard. 


The most common fleas infesting houses in the Eastern United 
States are the cosmopolitan dog and cat fleas, Ctenocephalus canis 

(fig. 90) and C. felis. Their life 
cycles will serve as typical. 
These two species have until 
recently been considered as one, 
under the name Pulex serraticeps. 
See figure 92. 

The eggs are oval, slightly 
translucent or pearly white, and 
measure about .5 mm. in their 
long diameter. They are de¬ 
posited loosely in the hairs of 
the host and readily drop off as the animal moves around. Howard 
found that these eggs hatch in one to two days. The larvae are 
elongate, legless, white, worm-like creatures. They are .exceed¬ 
ingly active, and avoid the light in every way possible. They 
east their first skin in from three to seven days and their second 
in from three to four days. They commenced spinning in from 
seven to fourteen days after hatching and the imago appeared 
five days later. Thus in summer, at Washington, the entire life 
cycle may be completed in about two weeks, (cf. fig. 91, 92). 

Strickland’s (1914) studies on the biology of the rat flea, Cerato- 
phyllus fasciatus, have so important a general bearing that we shall 
cite them in considerable detail. 

He found, to begin with, that there is a marked inherent range 
in the rate of development. Thus, of a batch of seventy-three eggs, 
all laid in the same day and kept together under the same condi- 



91. Larva of Xenopsylla cheopis. After Bacot and Ridewood. 


tions, one hatched in ten days; four in eleven days; twenty-five in 
twelve days; thirty-one in thirteen days; ten in fourteen days; one 
in fifteen days; and one in sixteen days. Within these limits the 
duration of the egg period seems to depend mainly on the degree 
of humidity. The incubation period is never abnormally prolonged 





Siplionaptera, or Fleas 


121 


as in the case of lice, (Warburton) and varying conditions of tempera¬ 
ture and humidity have practically no effect on the percentage of 
eggs which ultimately hatch. 

The same investigator found that the most favorable condition 
for the larva is a low temperature, combined with a high degree of 
humidity; and that the presence of rubbish in which the larva may 
bury itself is essential to its successful development. When larvae 
are placed in a bottle containing either wood-wool soiled by excre¬ 
ment, or with feathers or filter paper covered with dried blood they 



92. Head and pronotum of (a) deg flea; (b) of cat flea; (e) of hen flea. After Rothschild. 
( d ) Nycteridiphilus (Ishnopsyllus) hexactenus. After Oudemans. 


will thrive readily and pupate. They seem to have no choice be¬ 
tween dried blood and powdered rat feces for food, and also feed 
readily on flea excrement. They possess the curious habit of always 
devouring their molted skins. 

An important part of Strickland’s experiments dealt with the 
question of duration of the pupal stage under the influence of tempera¬ 
ture and with the longevity and habits of the adult. In October, 
he placed a batch of freshly formed cocoons in a small dish that was 
kept near a white rat in a deep glass jar in the laboratory. Two 
months later one small and feeble flea had emerged, but no more 
until February, four months after the beginning of the experiment. 
Eight cocoons were then dissected and seven more found to contain 
the imago fully formed but in a resting state. The remainder of 









122 


Parasitic Arthropoda 


the batch was then placed at 70° F. for one night, near a white 
rat. The next day all the cocoons were empty and the fleas were 
found on the white rat. 

Thus, temperature greatly influences the duration of the pupal 
period, which in Ceratophyllus fasciatus averages seventeen days. 
Moreover, when metamorphosis is complete a low temperature will 
cause the imago to remain within the cocoon. 

Sexually mature and ovipositing fleas, he fed at intervals and kept 
alive for two months, when the experiment was discontinued. In 
the presence of rubbish in which they could bury themselves, unfed 
rat fleas were kept alive for many months, whereas in the absence of 
any such substratum they rarely lived a month. In the former case, 
it was found that the length of life is influenced to some degree by the 
temperature and humidity. In an experiment carried out at 70° F. 
and 45 per cent humidity, the fleas did not live for more than four 
months, while in an experiment at 6o° F. and 70 per cent humidity 
they lived for at least seventeen months. There was no indication 
that fleas kept under these conditions sucked moisture from surround¬ 
ing objects, and those kept in bell jars, with an extract of flea-rubbish 
on filter paper, did not live any longer than those which were not so 
supplied. 

Curiously enough, although the rat is the normal host of Cerato¬ 
phyllus fasciatus, it was found that when given the choice these fleas 
would feed upon man in preference to rats. However, none of the 
fleas laid eggs unless they fed on rat blood. 

The experiments of Strickland on copulation and oviposition in 
the rat flea showed that fleas do not copulate until they are sexually 
mature and that, at least in the case of Ceratophyllus fasciatus, the 
reproductive organs are imperfectly developed for some time (more 
than a week) after emerging from the pupa. When mature, copula¬ 
tion takes place soon after the fleas have fed on their true host—the 
rat—but not if they have fed on a facultative host only, such as man. 
Copulation is always followed by oviposition within a very short, 
time. 

The effect of the rat’s blood on the female with regard to egg- 
laying, Strickland concludes, is stimulating rather than nutritive, 
as fleas that were without food for many months were observed to 
lay eggs immediately after one feed. Similarly, the male requires, 
the stimulus of a meal of rat’s blood before it displays any copulatory 
activity. 


Siphonaptera , or Fleas 


123 


Mitzmain (1910) has described in detail the act of biting on man, 
as observed in the squirrel flea, Ceratophyllus acutus. “The flea 
when permitted to walk freely on the arm selects a suitable hairy 
space where it ceases abruptly in its locomotion, takes a firm hold 
with the tarsi, projects its proboscis, and prepares to puncture the 
skin. A puncture is drilled by the pricking epipharynx, the saw¬ 
tooth mandibles supplementing the movement by lacerating the 
cavity formed. The two organs of the rostrum work alternately, 
the middle piece boring, while the two lateral elements execute a 
sawing movement. The mandibles, owing to their basal attach¬ 
ments, are, as is expressed by the advisory committee on plague 
investigations in India ( Journal of Hygiene , vol. 6, No. 4, p. 499), 
‘capable of independent action, sliding up and down but maintaining 
their relative positions and preserving the lumen of the aspiratory 
channel.’ The labium doubles back, the V-shaped groove of this 
organ guiding the mandibles on either side.’’ 

‘ ‘ The action of the proboscis is executed with a forward movement 
of the head and a lateral and downward thrust of the entire body. 
As the mouth-parts are sharply inserted, the abdomen rises simultane¬ 
ously. The hind and middle legs are elevated, resembling oars. 
The forelegs are doubled under the thorax, the tibia and tarsi resting 
firmly on the epidermis serve as a support for the body during the 
feeding. The maxillary palpi are retracted beneath the head and 
thorax. The labium continues to bend, at first acting as a sheath 
for the sawing mandibles, and as these are more deeply inserted, it 
bends beneath the head with the elasticity of a bow, forcing the 
mandibles into the wound until the maxillas are embedded in the skin 
of the victim. When the proboscis is fully inserted, the abdomen 
ceases for a time its lateral swinging.” 

“The acute pain of biting is first felt when the mandibles have 
not quite penetrated and subsequently during each distinct move¬ 
ment of the abdomen. The swinging of the abdomen gradually 
ceases as it becomes filled with blood. The sting of the biting 
gradually becomes duller and less sensitive as feeding progresses. 
The movements of the elevated abdomen grow noticeably feebler 
as the downward thrusts of the springy bow-like labium becomes less 
frequent.” 

“As the feeding process advances one can discern through the 
translucent walls of the abdomen a constant flow of blood, caudally 
from the pharynx, accompanied by a peristaltic movement. The 


124 


Parasitic Arthropoda 


end of the meal is signified in an abrupt manner. The flea shakes 
its entire body, and gradually withdraws its proboscis by lowering 
the abdomen and legs and violently twisting the head.” 

‘‘When starved for several days the feeding of the rat fleas is 
conducted in a rather vigorous manner. As soon as the proboscis 
is buried to the full length the abdomen is raised and there ensues a 
gradual lateral swaying motion, increasing the altitude of the raised 
end of the abdomen until it assumes the perpendicular. The flea is 
observed at this point to gain a better foothold by advancing the 
fore tarsi, and then, gradually doubling back the abdomen, it turns 
with extreme agility, nearly touching with its dorsal side the skin 
of the hand upon which it is feeding. Meanwhile, the hungry para¬ 
site feeds ravenously.” 

‘‘It is interesting to note the peculiar nervous action which the 
rodent fleas exhibit immediately when the feeding process is com¬ 
pleted or when disturbed during the biting. Even while the rostrum 
is inserted to the fullest the parasite shakes its head spasmodically; 
in a twinkling the mouth is withdrawn and then the flea hops away.” 

A habit of fleas which we shall see is of significance in considering 
their agency in the spread of bubonic plague, is that of ejecting blood 
from the anus as they feed. 

Fleas are famous for their jumping powers, and in control measures 
it is of importance to determine their ability along this line. It is 
often stated that they can jump about four inches, or, according to 
the Indian Plague Commission Xenopsylla cheopis cannot hop farther 
than five inches. Mitzmain (1910) conducted some careful experi¬ 
ments in which he found that the human flea, Pulex irritans, was 
able to jump as far as thirteen inches on a horizontal plane. The 
mean average of five specimens permitted to jump at will was seven 
and three-tenths inches. The same species was observed to jump 
perpendicularly to a height of at least seven and three-fourths inches. 
Other species were not able to equal this record. 

The effect of the bite of fleas on man varies considerably accord¬ 
ing to the individual susceptibility. According to Patton and Cragg, 
this was borne out in a curious manner by the experiments of Chick 
and Martin. ‘‘In these, eight human hosts were tried; in seven, 
little or no irritation was produced, while in one quite severe inflam¬ 
mation was set up around each bite.” Of two individuals, equally 
accustomed to the insects, going into an infested room, one may be 
literally tormented by them while the other will not notice them. 


Siphonaptera, or Fleas 


125 


Indeed it is not altogether a question of susceptibility, for fleas seem 
to have a special predilection for certain individuals. The typical 
itching wheals produced by the bites are sometimes followed, especi¬ 
ally after scratching, by inflammatory papules. 

The itching can be relieved by the use of lotions of carbolic acid 
(2-3 per cent), camphor, menthol lotion, or carbolated vaseline. 
If forced to sleep in an infested room, protection from attacks can 
be in a large measure gained by sprinkling pyre thrum, bubach, or 
California insect powder between the sheets. The use of camphor, 
menthol, or oil of eucalyptus, or oil of pennyroyal is also said to afford 
protection to a certain extent. 

In the Eastern United States the occurrence of fleas as household 
pests is usually due to infested cats and dogs which have the run of 
the house. We have seen that the eggs are not attached to the host 
but drop to the floor when they are laid. Verrill, cited by Osbom, 
states that on one occasion he was able to collect fully a teaspoonful 
of eggs from the dress of a lady in whose lap a half-grown kitten had 
been held for a short time. Patton and Cragg record seeing the 
inside of a hat in which a kitten had spent the night, so covered with 
flea eggs that it looked “as if it had been sprinkled with sugar from 
a sifter.” It is no wonder that houses in which pets live become 
overrun with the fleas. 

One of the first control measures, then, consists in keeping such 
animals out of the house or in rigorously keeping them free from fleas. 
The latter can best be accomplished by the use of strong tar soap 
or Armour’s “Flesope,” which may be obtained from most druggists. 
The use of a three per cent solution of creolin, approximately four 
teaspoonfuls to a quart of warm water, has also been recommended. 
While this is satisfactory in the case of dogs, it is liable to sicken cats, 
who will lick their fur in an effort to dry themselves. Howard 
recommends thoroughly rubbing into the fur a quantity of pyrethrum 
powder. This partially stupifies the fleas which should be promptly 
swept up and burned. 

He also recommends providing a rug for the dog or cat to sleep 
on and giving this rug a frequent shaking and brushing, afterwards 
sweeping up and burning the dust thus removed. 

Since the larvas of fleas are very susceptible to exposure, the use 
of bare floors, with few rugs, instead of carpets or matting, is to be 
recommended. Thorough sweeping, so as to allow no accumulation 
of dust in cracks and crevices will prove efficient. If a house is once 


126 


Parasitic Arthropoda 


infested it may be necessary to thoroughly scrub the floors with hot 
soapsuds, or to spray them with gasoline. If the latter method is 
adopted, care must be taken to avoid the possibility of fire. 

To clear a house of fleas Skinner recommends the use of flake 
naphthalene. In a badly infested house he took one room at a time, 
scattering on the floor five pounds of flake naphthalene, and closed 
it for twenty-four hours. It proved to be a perfect and effectual 
remedy and very inexpensive, as the naphthalene could be swept up 
and transferred to other rooms. Dr. Skinner adds, “so far as I am 
concerned, the flea question is solved and if I have further trouble 
I know the remedy. I intend to keep the dog and cat.” 

The late Professor Slingerland very effectively used hydrocyanic 
acid gas fumigation in exterminating fleas in houses. In one case, 
where failure was reported, he found on investigation that the house 
had become thoroughly reinfested from pet cats, which had been left 
untreated. Fumigation with sulphur is likewise efficient. 

The fact that adult fleas are usually to be found on the floor, 
when not on their hosts, was ingeniously taken advantage of by 
Professor S. H. Gage in ridding an animal room at Cornell University 
of the pests. He swathed the legs of a janitor with sticky fly-paper 
and had him walk back and forth in the room. Large numbers of 
the fleas were collected in this manner. 

In some parts of the southern United States hogs are commonly 
infested and in turn infest sheds, bams and even houses. Mr. H. E. 
Vick informs us that it is a common practice to turn sheep into barn- 
lots and sheds in the spring of the year to collect in their wool, the 
fleas which abound in these places after the hogs have been turned 
out. 

It is a common belief that adult fleas are attracted to fresh meat 
and that advantage of this can be taken in trapping them. Various 
workers, notably Mitzman (1910), have shown that there is no basis 
for such a belief. 

The true chiggers — The chigoes, or true chiggers, are the most 
completely parasitic of any of the fleas. Of the dozen or more known 
species, one commonly attacks man. • This is Dermatophilus penetrans, 
more commonly known as Sarcopsylla penetrans or Pulex penetrans. 

This species occurs in Mexico, the West Indies, Central and South 
America. There are no authentic records of its occurrence in the 
United States although,.as Baker has pointed out, there is no reason 


The True Chiggers 


127 


why it should not become established in Florida and Texas. It is 
usually believed that Brazil was its original home. Sometime about 
the middle of the nineteenth century it was introduced into West 
Africa and has spread across that continent. 

The males and the immature females of Dermatophilus penetrans 
(fig. 93) closely resemble those of other fleas. They are very active 
little brown insects about 1-1.2 mm. in size, which live in the dust of 
native huts and stables, and in dry, sandy soil. In such places they 
often occur in enormous numbers and become a veritable plague. 

They attack not only man but various animals. According to 
Castellani and Chalmers, “Perhaps the most noted feature is the way 



93. Dermatophilus penetrans. Much enlarged. After Karsten. 


in which it attacks pigs. On the Gold Coast it appeared to be largely 
kept in existence by these animals. It is very easily captured in 
the free state by taking a little pig with a pale abdomen, and placing 
it on its back on the ground on which infected pigs are living. After 
watching a few moments, a black speck will appear on the pig’s 
abdomen, and quickly another and another. These black specks are 
jiggers which can easily be transferred to a test tube. On examina¬ 
tion they will be found to be males and females in about equal 
numbers.” 

Both the males and females suck blood. That which characterizes 
this species as distinguished from other fleas attacking man is that 
when the impregnated female attacks she burrows into the skin 
and there swells until in a few days she has the size and appearance of 
a small pea (fig. 94). Where they are abundant, hundreds of the 





128 


Parasitic Arthropoda 



94. Dermatophilus penetrans, gravid female. After Moniez. 



pests may attack a single individual (fig. 95). Here they lie with the 
apex of the abdomen blocking the opening. According to Fulle- 

born (1908) they do not 
penetrate beneath the 
epidermis. The eggs are 
not laid in the flesh of 
the victim, as is some¬ 
times stated, but are 
expelled through this 
opening. The female 
then dies, withers and 
falls away or is expelled 
by ulceration. Accord¬ 
ing to Brumpt, she first 
quits the skin and then, 
falling to the ground, 
deposits her eggs. The 
subsequent develop¬ 
ment in so far as known, 
is like that of other fleas. 

The chigoe usually 
enters between the toes, 
the skin about the roots 
of the nails, or the soles 


95. Chiggers in the sole of foot of man. Manson’s 
Tropical Diseases. Permission of Cassell and Co. 











Siphonaptera, or Fleas 


129 


of the feet, although it may attack other parts of the body. Mense 
records the occurrence in folds of the epidermis, as in the neighbor¬ 
hood of the anus. They give rise to irritation 
and unless promptly and aseptically removed 
there often occurs pus formation and the 
development of a more or less serious abscess. 
Gangrene and even tetanus may ensue. 

Treatment consists in the careful removal 
of the insect, an operation more easily accom¬ 
plished a day or two after its entrance, than 
at first, when it is unswollen. The ulcerated 
point should then be treated with weak car¬ 
bolic acid, or tincture of iodine, or dusted 
thoroughly with an antiseptic powder. 

Castellani and Chalmers recommend as 
prophylactic measures, keeping the house clean and keeping pigs, 
poultry, and cattle away therefrom. “High boots should be used, 
and especial care should be taken not to go to a ground floor bath¬ 
room with bare feet. The feet, especially the toes, and under the 
nails, should be carefully examined every morning to see if any black 




97. Echidnophaga gallinacea infesting head of chicken. After Enderlein. 


dots can be discovered, when the jigger should be at once removed, 
and in this way suppuration will be prevented. It is advisable, 








130 


Parasitic Arthropoda 


also, to sprinkle the floors with carbolic lotion, Jeyes’ fluid, or with 
pyrethrum powder, or with a strong infusion of native tobacco, as 
recommended by Law and Castellani.” 

Echidnopliaga gallinacea (fig. 96) is a widely distributed Hectopsyl- 
lid attacking poultry (fig. 97). It occurs in the Southern and South¬ 
western United States and has been occasionally reported as attack¬ 
ing man, especially children. It is less highly specialized than 
Dermatophilus penetrans , and does not ordinarily cause serious 
trouble in man. 


CHAPTER IV 


ACCIDENTAL OR FACULTATIVE PARASITES 

In addition to the many species of Arthropods which are normally 
parasitic on man and animals, there is a considerable number of those 
which may be classed as accidental or facultative parasites. 

Accidental or facultative parasites are species which are normally 
free-living, but which are able to exist as parasites when accidentally 
introduced into the body of man or other animal. A wide range of 
forms is included under this grouping. 

Acarina 

A considerable number of mites have been reported as accidental 
or even normal, endoparasites of man, but the authentic cases are 
comparatively few. 

In considering such reports it is well to keep in mind von Siebold’s 
warning that in view of the universal distribution of mites one should 
be on his guard. In vessels in which animal and other organic 
fluids and moist substances gradually dry out, mites are very abund¬ 
antly found. If such vessels are used without very careful prelimi¬ 
nary cleaning, for the reception of evacuations of the sick, or for the 
reception of parts removed from the body, such things may be readily 
contaminated by mites, which have no other relation whatever to 
them. 

Nevertheless, there is no doubt but that certain mites, normally 
free-living, have occurred as accidental parasites of man. Of these 
the most commonly met with is Tyroglyphus siro, the cheese-mite. 

Tyroglyphus siro is a small mite of a whitish color. The male 
measures about 500^ long by 250^ wide, the female slightly larger. 
They live in cheese of almost any kind, especially such as is a little 
decayed. “The individuals gather together in winter in groups or 
heaps in the hollows and chinks of the cheese and there remain 
motionless. As soon as the temperature rises a little, they gnaw 
away at the cheese and reduce it to a powder. The powder is com¬ 
posed of excrement having the appearance of little grayish microscopic 
balls; eggs, old and new, cracked and empty; larvae, nymphs, and 
perfect mites, cast skins and fragments of cheese, to which must be 
added numerous spores of microscopic fungi.” — Murray. 


132 


Accidental or Facultative Parasites 


Tyroglyphus siro, and related species, have been found many 
times in human feces, under conditions which preclude the explana¬ 
tion that the contamination occurred outside of the body. They 
have been supposed to be the cause of dysentery, or diarrhoea, and 
it is probable that the Acarus dysenteries of Linnaeus, and Latreille, 
was this species. However, there is little evidence that the mites 
cause any noteworthy symptoms, even when taken into the body 
in large numbers. 

Histiogaster spermaticus (fig. 152) is a Tyroglyphid mite which 
was reported by Trouessart (1902) as having been found in a cyst 
in the groin, adherent to the testis. When the cyst was punctured, 
it yielded about two ounces of opalescent fluid containing spermatozoa 
and numerous mites in all stages of development. The evidence 
indicated that a fecundated female mite had been introduced into 
the urethra by means of an unclean catheter. Though Trouessart 
reported the case as that of a Sarcoptid, Banks places the genus 
Histiogaster with the Tyroglyphidae. He states that our species 
feeds on the oyster-shell bark louse, possibly only after the latter is 
dead, and that in England a species feeds within decaying reeds. 

Nephrophages sanguinarius is a peculiarly-shaped, angular mite 
which was found by Miyake and Scriba (1893) for eight successive 
days in the urine of a Japanese suffering from fibrinuria. Males, 
.117 mm. long by .079 mm. wide, females .36 mm. by .12 mm., 
and eggs were found both in the spontaneously emitted urine and in 
that drawn by means of a catheter. All the mites found were dead. 
The describers regarded this mite as a true endoparasite, but it is 
more probable that it should be classed as an accidental parasite. 

Myriapoda 

There are on record a number of cases of myriapods occurring as 
accidental parasites of man. The subject has been treated in detail 
by Blanchard (1898 and 1902), who diserrssed forty cases. Since 
then at least eight additions have been made to the list. 

Neveau-Lamaire (1908) lists thirteen species implicated, repre¬ 
senting eight different genera. Of the Chilognatka there are three, 
Julus terrestris, J. londinensis and Polydesmus complanatus. The 
remainder are Chilopoda, namely, Lithobius forficatus, L. malenops, 
Geophilus carpophagus , G. electricus, G. similis, G. cephalicus, Scutigera 
coleoptrata, Himantarium gervaisi, Cluetechelyne vesuviana and 
Stigniatogaster subterraneus. 


Myriapoda 


133 


The majority of the cases relate to infestation of the nasal fossae, 
or the frontal sinus, but intestinal infestation also occurs and there 
is one recorded case of the presence of a species in Julus (fig. 13) in 
the auditory canal of a child. 

In the nose, the myriapods have been known to live for months 
and according to some records, even for years. The symptoms 
caused by their presence are inflammation, with or without increased 
flow of mucus, itching, more or less intense headache, and at times 
general symptoms such as vertigo, delirium, convulsions, and the 
like. These symptoms disappear suddenly when the parasites are 
expelled. 

In the intestine of man, myriapods give rise to obscure symptoms 
suggestive of infestation by parasitic worms. In a case reported by 
Verdun and Bruyant (1912), a child twenty months of age had been 
affected for fifteen days by digestive disturbances characterized by 
loss of appetite, nausea and vomiting. The latter had been partic¬ 
ularly pronounced for three days, when there was discovered in the 
midst of the material expelled a living myriapod of the species 
Chcetechelyne vesuviana. Anthelminthics had been administered 
without result. In some of the other cases, the administration of 
such drugs had resulted in the expulsion of the parasite through the 
anus. 

One of the extreme cases on record is that reported by Shipley 
(1914). Specimens of Geoplulus gorizensis (= G. subterraneus) 
‘were vomited and passed by a woman of 68 years of age. Some of 
the centipedes emerged through the patient’s nose, and it must be 
mentioned that she was also suffering from a round worm. One of 
her doctors was of the opinion that the centipedes were certainly 
breeding inside the lady’s intestines, and as many as seven or eight, 
sometimes more, were daily leaving the alimentary canal.” 

‘‘According to her attendant’s statements these centipedes had 
left the body in some hundreds during a period of twelve or eighteen 
months. Their presence produced vomiting and some hsematemesis, 
and treatment w r ith thymol, male-fern and turpentine had no effect 
in removing the creatures.” 

The clinical details, as supplied by Dr. Theodore Thompson were 
as follows: 

‘‘Examined by me July, 1912, her tongue was dry and glazed. 
There was bleeding taking place from the nose and I saw a living 
centipede she had just extracted from her nostril. Her heart, lungs 


i34 


Accidental or Facultative Parasites 


and abdomen appeared normal. She was not very wasted, and did 
not think she had lost much flesh, nor was there any marked degree 
of anemia.” 

Shipley gives the following reasons for believing it impossible 
that these centipedes could have multiplied in the patient’s intestine. 
‘‘The breeding habits of the genus Geophilus are peculiar, and ill 
adapted for reproducing in such a habitat. The male builds a small 
web or nest, in which he places his sperm, and the female fertilizes 
herself from this nest or web, and when the eggs are fertilized they 
are again laid in a nest or web in which they incubate and in two or 
three weeks hatch out. The young Geophilus differ but very little 
from the adult, except in size. It is just possible, but improbable, 
that a clutch of eggs had been swallowed by the host when eating 
some vegetables or fruit, but against this is the fact that the Geophilus 
does not lay its eggs upon vegetables or fruit, but upon dry wood or 
earth. The egg-shell is very tough and if the eggs had been swallowed 
the egg-shells could certainly have been detected if the dejecta were 
examined. The specimens of the centipede showed very little signs 
of being digested, and it is almost impossible to reconcile the story 
of the patient with what one knows of the habits of the centipedes.” 

In none of the observed cases have there been any clear indica¬ 
tions as to the manner of infestation. It is possible that the myria¬ 
pods have been taken up in uncooked fruit or vegetables. 

Lepidopterous Larvae 

Scholeciasis — Hope (1837) brought together six records of infesta¬ 
tion of man by lepidopterous larvae and proposed to apply the name 
scholeciasis to this type of parasitism. The clearest case was that 
of a young boy who had repeatedly eaten raw cabbage and who 
vomited larva; of the cabbage butterfly, Pieris brassiere. Such cases 
are extremely rare, and there are few reliable data relative to the 
subject. In this connection it may be noted that Spuler (1906) has 
described a moth whose larvae live as ectoparasites of the sloth. 

COLEOPTERA 

Canthariasis —By this term Hope designated instances of acci¬ 
dental parasitism by the larvae or adults of beetles. Reports of 
such cases are usually scouted by parasitologists but there seems no 
good basis for wholly rejecting them. Cobbold refers to a half 
dozen cases of accidental parasitism by the larvae of Flaps mortisaga. 



Dipterous Larvae 


i35 


In one of these cases upwards of 1200 larvae and several perfect 
insects were said to have been passed per anum. French (1905) 

reports the case of a man 
who for a considerable period 
voided adult living beetles 
of the species Nitidula 
bipustulata. Most of the 
other cases on record relate 
to the larvae of Dermestidce 
(larder beetles et al .) or 
Infestation probably occurs 
through eating raw or imperfectly cooked foods containing eggs or 
minute larvae of these insects. 

Brumpt cites a curious case of accidental parasitism by a coleopter¬ 
ous larva belonging to the genus Necrobia. This larva was extracted 
from a small tumor, several millimeters long, on the surface of the 
conjunctiva of the eye. The larvae of this genus ordinarily live in 
decomposing flesh and cadavers. 

Dipterous Larvae 

Myasis— By this term (spelled also myiasis, and myiosis), is 
meant parasitism by dipterous larvae. Such parasitism may be 
normal, as in the cases already described under the heading parasitic 
Diptera, or it may be facultative, due to free-living larvae being 
accidentally introduced 
into wounds or the body- 
cavities of man. Of this 
latter type, there is a 
multitude of cases on 
record, relating to com¬ 
paratively few species. 

The literature of the sub¬ 
ject, like that relating 
to facultative parasitism 
in general, is unsatis¬ 
factory, for most ot the 

determinations of species 99 . Piophila casei. After Graham-Smith. 

have been very loose. 

Indeed, so little has been known regarding the characteristics of 
the larvae concerned that in many instances they could not be exactly 




98. Larva of Piophila casei. Caudal aspect of larva. 
Posterior stigmata. 


Tenebrionidce (meal infesting species). 




136 


Accidental or Facultative Parasites 


determined. Fortunately, several workers have undertaken com¬ 
parative studies along this line. The most comprehensive publica¬ 
tion is that of Banks (1912), entitled “The structure of certain dip¬ 
terous larvae, with particular reference to those in human food.” 

Without attempting an exhaustive list, we shall discuss here the 
more important species of Diptera whose larvae are known to cause 
myasis, either external or internal. The following key will serve 
to determine those most likely to be encountered. The writers 
would be glad to examine specimens not readily identifiable, if 
accompanied by exact data relative to occurrence. 

a. Body more or less flattened, depressed; broadest in the middle, each segment 

with dorsal, lateral, and ventral fleshy processes, of which the laterals, 
at least, are more or less spiniferous (fig. 101). Fannia ( = Homalomyia). 
In F. canicularis the dorsal processes are nearly as long as the laterals; 
in F. scalaris the dorsal processes are short spinose tubercles. 
aa. Body cylindrical, or slender conical tapering toward the head; without 
fleshy lateral processes (fig. 105). 

b. With the posterior stigmata at the end of shorter or longer tubercles, or if not 

placed upon tubercles, then not in pit; usually without a “marginal button” 
and without a chitinous ring surrounding the three slits; the slits narrowly 
or broadly oval, not bent (fig. 171 i). Acalyptrate muscidce and some species 
of Anthomyiidce. To this group belong the cheese skipper ( Piophila casei, 
figs. 98, 99), the pomace-fly ( Drosophila ampelophila) , the apple maggot 
(Rhagoletis pomonella) , the cherry fruit fly ( Rhagoletis cingulata ), the small 
dung fly ( Sepsis violacea, fig. 170), the beet leaf-miner ( Pegomyia vicina, 
fig. 171 i), the cabbage, bean and onion maggots ( Pliorbia spp.) et. al. 
bb. Posterior stigmata of various forms, if the slits are narrowly oval (fig. 171) 
then they are surrounded by a chitin ring which may be open ventro- 
mesally. 

c. Integument leathery and usually strongly spinulose; larvae hypodermatic or 

endoparasitic.Bot flies (fig. 171, f, g, k). — Oestridce 

cc. Integument not leathery and (except in Protocalliphora ) spinulse restricted 
to transverse patches near the incisures of the segments. 

d. The stigmal plates in a pit; the lip-like margin of the pit with a number of 

fleshy tubercles; chitin of the stigma not complete; open ventro-mesally, 

button absent (fig. 171 e).Flesh flies. — Sarcophaga 

dd. Stigmata not in a pit. 

e. The chitin ring open ventra-mesally; button absent (fig. 171 c). Screw- 

worm fly . Chrysomyia 

ee. The chitin ring closed. 

/. vSlits of the posterior stigmata straight; marginal “button” present (fig. 171 b); 
two distinct mouth hooks, fleshy tubercles around the anal area. Phormia 
(fig. 171 f), Lucilia and Calliphora (fig. 172, a, b), Protocalliphora (fig. 171, j), 
Cynomyia (fig. 171, a). Blow flies, bluebottle flies . Calliphorince 






Dipterous Larva 


i37 


//. Slits of the posterior stigmata sinuous or bent. Subfamily Muscinae. 
g. Slits of the posterior stigmata bent; usually two mouth hooks. Muscina 
stabulans (fig. 171, /), Muscina similis, Myiospila meditatunda (fig. 172, i), 
and some of the higher Anthomyiidce. 

gg. Slits of the posterior stigmata sinuous; mouth hooks usually consolidated 
into one. The house-fly ( Musca domestica fig. 171, d), the stable fly 
(Stomoxys calcitrans) the horn fly ( Lyperosia irritans), Pyrellia, Psendo- 
pyrellia, Morellia, Mesembrina. Polietes, et. al. (fig. 172 in part). 

Eristalis — The larvse of Eristalis are the so-called rat-tailed mag¬ 
gots, which develop in foul water. In a few instances these larvae 
have been known to pass through the human alimentary canal 
uninjured. Hall and Muir (1913) report the case of a boy five years 
of age, who had been ailing for ten weeks and who was under treat¬ 
ment for indigestion and chronic constipation. For some time he 
had vomited everything he ate. On administration of a vermifuge 
he voided one of the rat-tailed maggots of Eristalis. He admitted 
having drunk water from a ditch full of all manner of rotting matter. 
It was doubtless through this that he became infested. It is worth 
noting that the above described symptoms may have been due to 
other organisms or substances in the filthy water. 

Piophila casei, the cheese-fly (fig. 99), deposits its eggs not only 
in old cheeses, but on ham, bacon, and other fats. The larvae (fig. 98) 
are the well-known cheese skippers, which sometimes occur in great 
abundance on certain kinds of cheese. Indeed, some people have 
a comfortable theory that such infested cheese is especially good. 
Such being the case, it is small wonder that this species has been 
repeatedly reported as causing intestinal myasis. Thebault (1901) 
describes the case of a girl who, shortly after consuming a large piece 
of badly infested cheese, became ill and experienced severe pains 
in the region of the navel. Later these extended through the entire 
alimentary canal, the excrement was mixed with blood and she 
suffered from vertigo and severe headaches. During the four fol¬ 
lowing days the girl felt no change, although the excretion of the blood 
gradually diminished and stopped. On the fourth day she voided 
two half-digested larvae and, later, seven or eight, of which two were 
alive and moving. 

That these symptoms may be directly attributed to the larvae, 
or “skippers,”has been abundantly shown by experimental evidence. 
Portschinsky cites the case of a dog fed on cheese containing the 
larvae. The animal suffered much pain and its excrement contained 
blood. On post mortem it was found that the small intestine through- 


133 


Accidental or Facultative Parasites 


out almost its entire length was marked by bloody bruises. The 
papillse on these places were destroyed, although the walls were 
not entirely perforated. In the appendix were found two or three 
dead larvae. Alessandri (1910) has likewise shown that the larvae 
cause intestinal lesions. 

According to Graham-Smith, Austen (1912) has recorded a case 
of myasis of the nose, attended with a profuse watery discharge of 
several weeks duration and pain, due to the larvae of Piophila casei. 

Anthyomyiidae—The characteristic larvae of two species of Fannia 
( = Homalomyia or Anthomyia, in part) (fig. 101) are the most com¬ 


monly reported of dip¬ 
terous larvae causing intes¬ 
tinal myasis. Hewitt 
(1912) has presented a 
valuable study of the bio¬ 
nomics and of the larvae 
of these flies, a type of 
what is needed for all the 
species concerned in my¬ 
asis. We have seen two 
cases of their having been 



100. Fannia canicularis (x4). After Graham-Smith. 


passed in stools, without having caused any special symptoms. 
In other instances their presence in the alimentary canal has given 
rise to symptoms vaguely described as those of tapeworm infestation, 
or helminthiasis. More specifically, they have been described as 
causing vertigo, severe headache, nausea and vomiting, severe 
abdominal pains, and in some instances, bloody diarrhoea. 

One of the most striking cases is that reported by Blankmeyer 
(1914), of a woman whose illness began fourteen years previously 
with nausea and vomiting. After several months of illness she began 
passing larvae and was compelled to resort to enemas. Three years 
previous to the report, she noticed frequent shooting pains in the 
rectal region and at times abdominal tenderness was marked. There 
was much mucus in the stools and she “experienced the sensation 
of larvae crawling in the intestine.” Occipital headaches were 
marked, with remissions, and constipation became chronic. The 
appetite was variable, there was a bad taste in the mouth, tongue 
furred and ridged, and red at the edges. Her complexion was sal¬ 
low, and general nervousness was marked. As treatment, there 
were given doses of magnesium sulphate before breakfast and at 




A nthyomyiidce 


i39 


4 p. m. , with five grain doses of salol four times a day. The customary 
parasiticides yielded no marked benefit. At the time of the report 
the patient passed from four to fifty larvae per day, and was showing 
some signs of improvement. The nausea had disappeared, her 
nervousness was less evident, and there was a slight gain in weight. 

The case was complicated by various other disorders, but the 
symptoms given above seem to be in large part attributable to the 
myasis. There is nothing in the case to justify the assumption 
that larvae were continuously present, for years. It seems more 
reasonable to suppose that something in the habits of the patient 
favored repeated infestation. Nevertheless, a study of the various 
cases of intestinal myasis caused by these and 
other species of dipterous larvae seems to indi¬ 
cate that the normal life cycle may be con¬ 
siderably prolonged under the unusual conditions. 

The best authenticated cases of myasis of the 
urinary passage have been due to larvae of 
Fannia. Chevril (1909) collected and described 
twenty cases, of which seven seemed beyond 
doubt. One of these was that of a woman of 
fifty-five who suffered from albuminuria, and 
urinated with much difficulty, and finally passed 
thirty to forty larvae of Fannia canicularis. 

It is probable that infestation usually occurs 
through eating partially decayed fruit or vege¬ 
tables on which the flies have deposited their 
eggs. Wellman points out that the flies may 
deposit their eggs in or about the anus of 
persons using outside privies and Hewitt 
believes that this latter method of infection is probably the common 
one in the case of infants belonging to careless mothers. “Such 
infants are sometimes left about in an exposed and not very clean 
condition, in consequence of which flies are readily attracted to them 
and deposit their eggs.” 

Muscinae—The larvae of the common house-fly, Mnsca domestica, 
are occasionally recorded as having been passed with the feces or 
vomit of man. While such cases may occur, it is probable that in 
most instances similar appearing larvae of other insects have been 
mistakenly identified. 



101. Larva of Fannia 
scalaris. 










Accidental or Facultative Parasites 


140 


Muscina stabulans is re¬ 
garded by Portschinsky 
(1913) as responsible for 
many of the cases of intesti¬ 
nal mvasis attributed to other 
species. He records the case 
of a peasant who suffered from 
pains in the lower part of the 
breast and intestines, and 
whose stools were mixed with 
blood. F rom N ovember until 
March he had felt particu¬ 
larly ill, being troubled with 
nausea and vomiting in addi¬ 
tion to the pain in his intestines. In March, his physician prescribed 
injections of a concentrated solution of tannin, which resulted in the 
expulsion of fifty living larvae of Muscina stabulans. Thereafter 
the patient felt much better, although he suffered from intestinal 
catarrh in a less severe form. 

Calliphorinae — Closely related to the Sarcophagidae are the 
Calliphorince. to which group belong many of the so-called “blue 
bottle” flies. Their larvae feed upon dead animals, and upon fresh 
and cooked meat. Those of Pro- 
tocalliphora, already mentioned, 
are ectoparasitic on living nestling 
birds. Larvae of Lucilia, we have 
taken from tumors on living turtles. 

To this sub-family belongs also 
Auchqromyia luteola, the Congo 
floor maggot. Some of these, 
and at least the last mentioned, 
are confirmed, rather than faculat- 
tive parasites. Various species of 
Calliphorinae are occassionally met 
with as facultative parasites of 

103. Lucilia caesar, (x 3 ). After Howard. 

man. 

Chrysomyia macellaria, the screw worm fly (fig. 107), is the fly 
which is responsible for the most serious cases of human myasis in 
the United States. It is widely distributed in the United States 




102. Muscina stabulans (X4). After Graham 
Smith. 


Chrysomyia macellaria 


141 

but is especially abundant in the south. While the larvas b ] n 
decaying matter in general, they so commonly breed in the living 
flesh of animals that they merit rank as true parasites. The females 
are attracted to open wounds of all kinds on cattle and other animals 
and quickly deposit large numbers of eggs. Animals which have 
been recently castrated, dehorned, or branded, injured by barbed 
wire, or even by the attacks of ticks are promptly attacked in the 
regions where the fly abounds. Even the navel of young calves or 
discharges from the vulva of cows may attract the insect. 

Not infrequently the fly attacks man, being attracted by an of¬ 
fensive breath, a chronic catarrh, or a purulent discharge from the 
ears. Most common are the cases where the eggs are deposited in 



104. Calliphora erythrocephala, (x6). After Graham-Smith. 


the nostrils. The larvae, which are hatched in a day or two, are 
provided with strong spines and proceed to bore into the tissues 
of the nose, even down into or through the bone, into the frontal 
sinus, the pharynx, larynx, and neighboring parts. 

Osborn (1896) quotes a number of detailed accounts of the attacks 
of the Chrysomyia on man. A vivid picture of the symptomology 
of rhinal myasis caused by the larvae of this fly is given by Castellani 
and Chalmers: “Some couple of days after a person suffering from 
a chronic catarrh, foul breath, or ozacna, has slept in the open or has 
been attacked by a fly when riding or driving, — i.e., when the hands 
are engaged — signs of severe catarrh appear, accompanied with 
inordinate sneezing and severe pain over the root of the nose or the 
frontal bone. Quickly the nose becomes swollen, and later the face 
also may swell, while examination of the nose may show the presence 








142 


Accidental or Facultative Parasites 


of the larvae. Left untreated, the patient rapidly becomes worse, 
and pus and blood are discharged from the nose, from which an 
offensive odor issues. Cough appears as well as fever, and often 
some delirium. If the patient lives long enough, the septum of the 
nose may fall in, the soft and hard palates may be pierced, the wall 
of the pharynx may be destroyed. By this time, however, the course 
of the disease will have become quite evident by the larvae dropping 
out of the nose, and if the patient continues to live all the larvae 
may come away naturally.” 

For treatment of rhinal myasis these writers recommend douch¬ 
ing the nose with chloroform water or a solution of chloroform in 
sweet milk (10-20 per cent), followed by douches of mild antiseptics. 
Surgical treatment may be necessary. 




Sarcophagidae —The larvae (fig. 105) of flies of this family usually 
feed upon meats, but have been found in cheese, oleomargerine, 
pickled herring, dead and living insects, cow dung and human feces. 
Certain species are parasitic in insects. Higgins (1890) reported 
an instance of “hundreds” of larvae of Sarcophaga being vomited by a 
child eighteen months of age. There was no doubt as to their origin 
for they were voided while the physician was in the room. There 
are many other reports of their occurrence in the alimentary canal. 
We have recorded elsewhere (Riley, 1906) a case in which some ten 
or twelve larvae of Sarcophaga were found feeding on the diseased 
tissues of a malignant tumor. The tumor, a melanotic sarcoma, 
was about the size of a small walnut, and located in the small of the 
back of an elderly lady. Although they had irritated and caused a 
slight hemorrhage, neither the patient nor others of the family knew 




SarcophagidcB 


143 


of their presence. Any discomfort which they had caused had been 
attributed to the sarcomatous growth. The infestation occurred 



106. A flesh fly (Sarcophaga), (X 4 ). After Graham-Smith. 


in mid-summer. It is probable that the adult was attracted by the 
odor of the discharges and deposited the living maggots upon the 
diseased tissues. 

According to Kiichenmeister, Sarcophaga carnaria (fig. 106), 
attracted by the odor, deposits its eggs and larvae in the vagina of 
girls and women when they lie naked in hot summer days upon dirty 
clothes, or when they have a discharge from the vagina. In malig¬ 
nant inflammations of the eyes the larvae 
even nestle under the eyelids and in 
Egypt, for example, produce a very 
serious addition to the effects of small¬ 
pox upon the cornea, as according to 
Pruner, in such cases perforation of the 
cornea usually takes place. 

Wohlfartia magnifica is another 
Sarcophagid which commonly infests 
man in the regions where it is abun¬ 
dant. It is found in all Europe but is 
especially common in Russia, where 
Portschinsky has devoted much atten¬ 
tion to its ravages. It deposits living 
larvse in wounds, the nasal fossae, the 
ears and the eyes, causing injuries 
even more revolting than those described for Chrysomyia. 







CHAPTER V 


ARTHROPODS AS SIMPLE CARRIERS OF DISEASE 

The fact that certain arthropods are poisonous, or may affect the 
health of man as direct parasites has always received attention in 
the medical literature. We come now to the more modern aspect 
of our subject,—the consideration of insects and other arthropods 
as transmitters and disseminators of disease. 

The simplest way in which arthropods may function in this 
capacity is as simple carriers of pathogenic organisms. It is con¬ 
ceivable that any insect which has access to, and comes in contact 
with such organisms and then passes to the food, or drink, or to the 
body of man, may in a wholly accidental and incidental manner 
convey infection. That this occurs is abundantly proved by the 
work of recent years. We shall consider as typical the case against 
the house-fly, which has attracted so much attention, both popular 
and scientific. The excellent general treatises of Hewitt (1910), 
Howard (1911), and Graham-Smith (1913), and the flood of bulletins 
and popular literature render it unnecessary to consider the topic 
in any great detail. 

The House-fly as a Carrier of Disease 

Up to the past decade the house-fly has usually been regarded as a 
mere pest. Repeatedly, however, it had been suggested that it 
might disseminate disease. We have seen that as far back as the 
sixteenth century, Mercurialis suggested that it was the agent in the 
spread of bubonic plague, and in 1658, Kircher reiterated this view. 
In 1871, Leidy expressed the opinion that flies were probably a means 
of communicating contagious diseases to a greater degree than was 
generally suspected. From what he had observed regarding gangrene 
in hospitals, he thought flies should be carefully excluded from 
wounds. In the same year, the editor of the London Lancet, referring 
to the belief that they play a useful role in purifying the air said, 
“Far from looking upon therh as dipterous angels dancing attendance 
on Hygeia, regard them rather in the light of winged sponges spread¬ 
ing hither and thither to carry out the foul behests of Contagion.” 

These suggestions attracted little attention from medical men, for 
it is only within very recent years that the charges have been sup¬ 
ported by direct evidence. Before considering this evidence, it is 

144 



The House-fly as a Carrier of Disease 


i45 


necessary that we define what is meant by “house-fly” and that we 
then consider the life-history of the insect. 

There are many flies which are occasionally to be found in houses, 
but according to various counts, from 95 per cent to 99 per cent of 
these in warm weather in the Eastern United States belong to the 
one species Musca domestica (fig. 108). This is the dominant house¬ 
fly the world over and is the one which merits the name. It has been 
well characterized by Schiner (1864), whose description has been 
freely translated by Hewitt, as follows: 

“ Frons of male occupying a fourth part of the breadth of the head. 
Frontal stripe of female narrow in front, so broad behind that it 
entirely fills up the width of the frons. The dorsal region of the 
thorax dusty grey in color with four equally broad longitudinal 
stripes. Scutellum gray with black sides. The light regions of 
the abdomen yellowish, transparent, the darkest parts at least at 
the base of the ventral side yellow. The last segment and a dorsal 
line blackish brown. Seen from behind and against the light, the 
whole abdomen shimmering yellow, and only on each side of the 
dorsal line on each segment a dull transverse band. The lower part 
of the face silky yellow, shot with blackish brown. Median stripe 
velvety black. Antennas brown. Palpi black. Legs blackish 
brown. Wings tinged with pale gray with yellowish base. The 
female has a broad velvety back, often reddishly shimmering frontal 
stripe, which is not broader at the anterior end than at the bases of 
the antennas, but become so very much broader above that the light 
dustiness of the sides is entirely obliterated. The abdomen gradu¬ 
ally becoming darker. The shimmering areas on the separate seg¬ 
ments generally brownish. All the other parts are the same as in 
the male.” 

The other species of flies found in houses in the Eastern United 
States which are frequently mistaken for the house or typhoid fly 
may readily be distinguished by the characters of the following key: 

a. Apical cell (R s ) of the wide wing open, i.e., the bounding veins 
parallel or divergent (fig. 100). Their larvae are flattened, the 
intermediate body segments each fringed with fleshy, more or 
less spinose, processes. Fannia 

b. Male with the sides of the second and third abdominal seg¬ 
ments translucent yellowish. The larva with three pairs 
of nearly equal spiniferous appendages on each segment, 



146 Arthropods as Simple Carriers of Disease 

arranged in a longitudinal series and in addition two pairs 
of series of smaller processes (fig. 100) F. canicidaris 
bb. Male with blackish abdomen, middle tibia with a tubercle 
beyond the middle. The larva with spiniferous appen¬ 
dages of which the dorsal and ventral series are short, the 
lateral series long and feathered (fig. 101). . . .F.scalaris 
aa. Apical cell (R) of the wing more or less narrowed in the 
margin; i. e., the bounding veins more or less converging 
(fig. 108). 

b. The mouth-parts produced and pointed, fitted for piercing, 

c. Palpi much shorter than the proboscis; a brownish gray 
fly, its thorax with three rather broad whitish stripes; 
on each border of the middle stripe and on the mesal 
borders of the lateral stripes is a blackish brown line. 
Abdomen yellowish brown; on the second, third and 
fourth segments are three brown spots which may be 
faint or even absent. The larvae live in dung. The 

stable-fly (fig. no). Stomoxys calcitrans 

cc. Palpi nearly as long as the proboscis. Smaller species 
than the house-fly. The horn-fly (fig. 167) 

Hcematohia irritans 

bb. Mouth-parts blunt, fitted for lapping. 

c. Thorax, particularly on the sides and near the base of the 
wings with soft golden yellow hairs among the bristles. 
This fly is often found in the house in very early spring 
or even in the winter. The cluster-fly, Pollenia rudis 
cc. Thorax without golden yellow hairs among the bristles, 

d. The last segment of the vein M with an abrupt 
angle, (fig. 108). The larvae live in manure, 

etc.House-fly, Musca domestica 

dd. The last segment of vein M with a broad, gentle 
curve (fig. 102). 

e. Eyes microscopically hairy; each abdominal 
segment with two spots. Larvae in dung. 

Myiospila meditahunda 

ee. Eyes bare ; abdomen gray and brown marbled. 

Muscina 

f. With black legs and palpi. M. assimilis 





The House-fly as a Carrier of Disease 


147 


ff. With legs more or less yellowish; palpi 
yellow. Larvae in decaying vegetable 
substances, dung, etc. M. stabulans 

It is almost universally believed that the adults of Musca domestica 
hibernate, remaining dormant throughout the winter in attics, 
around chimneys, and in sheltered but cold situations. This belief 
•has been challenged by Skinner (1913), who maintains that all the 
adult flies die off during the fall and early winter and that the species 
is carried over in the pupal stage, and in no other way. The cluster- 
fly, Pollenia rudis, undoubtedly does hibernate in attics and similar 



108. The house or typhoid fly (Musca domestica ( 4 .x)). After Howard. 

situations and is often mistaken for the house-fly. In so far as 
concerns Musca domestica, the important question as to hibernation 
in the adult stage is an open one. Many observations by one of the 
writers (Johannsen) tend to confirm Dr. Skinner’s conclusion, in so 
far as it applies to conditions in the latitude of New York State. 
Opposed, is the fact that various experimentors, notably Hewitt 
(1910) and Jepson (1909) wholly failed to carry pupae through the 
winter. 

The house-fly breeds by preference in horse manure. Indeed, 
Dr. Howard, whose extensive studies of the species especially qualify 
him for expressing an opinion on the subject, has estimated that under 
ordinary city and town conditions, more than ninety per cent of the 
flies present in houses have come from horse stables or their vicinity. 
They are not limited to such localities, by any means, for it has been 
found that they would develop in almost any fermenting organic 
substance. Thus, they have been bred from pig, chicken, and cow 



148 Arthropods as Simple Carriers of Disease 

manure, dirty waste paper, decaying vegetation, decaying meat, 
slaughter-house refuse, sawdust-sweepings, and many other sources. 
A fact which makes them especially dangerous as disease-carriers 
is that they breed readily in human excrement. 

The eggs are pure white, elongate ovoid, somewhat broader at 
the anterior end. They measure about one millimeter (1-25 inch) 
in length. They are deposited in small, irregular clusters, one 
hundred and twenty to one hundred and fifty from a single fly. A 
female may deposit as many as four batches in her life time. The 
eggs hatch in from eight to twenty-four hours. 

The newly hatched larva, or maggot (fig. 108), measures about two 
millimeters (1-12 inch) in length. It is pointed at the head end and 
blunt at the opposite end, where the spiracular openings are borne. 
It grows rapidly, molts three times and reaches maturity in from six 
to seven days, under favorable conditions. 

The pupal stage, like that of related flies, is passed in the old 
larval skin which, instead of being molted, becomes contracted and 
heavily chitinized, forming the so-called puparium (fig. 108). The 
pupal stage may be completed in from three to six days. 

Thus during the warm summer months a generation of flies may 
be produced in ten to twelve days. Hewitt at Manchester, England, 
found the minimum to be eight days but states that larvas bred in 
the open air in horse manure which had an average daily temperature 
of 22.5 C., occupied fourteen to twenty days in their development, 
according to the air temperature. 

After emergence, a period of time must elapse before the fly is 
capable of depositing eggs. This period has been termed the pre- 
oviposition period. Unfortunately we have few exact data regarding 
this period. Hewitt found that the flies became sexually mature in 
ten to fourteen days after their emergence from the pupal state and 
four days after copulation they began to deposit their eggs ; in other 
words the preoviposition stage was fourteen days or longer. Griffith 
(1908) found this period to be ten days. Dr. Howard believes that 
the time “must surely be shorter, and perhaps much shorter, under 
midsummer conditions, and in the freedom of the open air.’’ He 
emphasizes that the point is of great practical importance, since it is 
during this period that the trapping and other methods of destroying 
the adult flies, will prove most useful. 

Howard estimates that there may be nine generations of flies a 
year under outdoor conditions in places comparable in climate to 



The House-fly as a Carrier of Disease 149 

Washington. The number may be considerably increased in warmer 
climates. 

The rate at which flies may increase under favorable conditions is 
astounding. Various writers have given estimates of the numbers of 
flies which may develop as the progeny of a single individual, provid¬ 
ing all the eggs and all the individual flies survived. Thus, Howard 
estimates that from a single female, depositing one hundred and 
twenty eggs on April 15th, there may be by September 10th, 
5,598,720,000,000 adults. Fortunately, living forms do not produce 
in any such mathematical manner and the chief value of the figures 
is to illustrate the enormous struggle for existence which is con¬ 
stantly taking place in nature. 

Flies may travel for a considerable distance to reach food and 
shelter, though normally they pass to dwellings and other sources 
of food supply in the immediate neighborhood of their breeding 
places. Copeman, Howlett and Merriman (1911) marked flies by 
shaking them in a bag containing colored chalk. Such flies were 
repeatedly recovered at distances of eight to one thousand yards 
and even at a distance of seventeen hundred yards, nearly a mile. 

Hindle and Merriman (1914) continued these experiments on a 
large scale at Cambridge, England. They “do not think it likely 
that, as a rule, flies travel more than a quarter of a mile in thickly- 
housed areas.” In one case a single fly was recovered at a distance 
of 770 yards but a part of this distance was across open fen-land. 
The surprising fact was brought out that flies tend to travel either 
against or across the wind. The actual direction followed may be 
determined either directly by the action of the wind (positive anemo- 
tropism), or indirectly owing to the flies being attracted by any odor 
that it may convey from a source of food. They conclude that it is 
likely that the chief conditions favoring the disposal of flies are fine 
weather and a warm temperature. The nature of the locality is 
another considerable factor. Hodge (1913) has shown that when 
aided by the wind they may fly to much greater distances over the 
water. He reports that at Cleveland, Ohio, the cribs of the water 
works, situated a mile and a quarter, five miles, and six miles out in 
Lake Erie are invaded by a regular plague of flies when the wind 
blows from the city. Investigation showed that there was absolutely 
nothing of any kind in which flies could breed on the crib. 

The omnivorous habits of the house-fly are matters of everyday 
observation. From our view point, it is sufficient to emphasize 


150 Arthropods as Simple Carriers of Disease 

that from feeding on excrement, on sputum, on open sores, or on 
putrifying matter, the flies may pass to the food or milk upon the table 
or to healthy mucous membranes, or uncontaminated wounds. 
There is nothing in its appearance to tell whether the fly that comes 
blithely to sup with you is merely unclean, or whether it has just 
finished feeding upon dejecta teeming with typhoid bacilli. 



109. Pulvillus of foot of house-fly, showing glandular hairs. 


The method of feeding of the house-fly has an important bearing 
on the question of its ability to transmit pathogenic organisms. 
Graham-Smith (1910) has shown that when feeding, flies frequently 
moisten soluble substances with “vomit” which is regurgitated from 
the crop. This is, of course, loaded with bacteria from previous 
food. When not sucked up again these drops of liquid dry, and pro¬ 
duce round marks with an opaque center and rim and an intervening 
less opaque area. Fly-specks, then, consist of both vomit spots 
and feces. Graham-Smith shows a photograph of a cupboard window 
where, on an area six inches square, there were counted eleven hundred 
and two vomit marks and nine fecal deposits. 




The House-fly as a Carrier of Disease 151 

From a bacteriologist’s viewpoint a discussion of the possibility 
of a fly’s carrying bacteria would seem superfluous. Any exposed 
object, animate or inanimate, is contaminated by bacteria and will 
transfer them if brought into contact with suitable culture media, 
whether such substance be food, or drink, open wounds, or the sterile 
culture media of the laboratory. A needle point may convey enough 
germs to produce disease. Much more readily may the house-fly 
with its covering of hairs and its sponge-like pulvilli (fig. 109) pick 
up and transfer bits of filth and other contaminated material. 

For popular instruction this inevitable transfer of germs by the 
house-fly is strikingly demonstrated by the oft copied illustration 
of the tracks of a fly on a sterile culture plate. Two plates of gela¬ 
tine or, better, agar medium are prepared. Over one of these a fly 
(with wings clipped) is allowed to walk, the other is kept as a check. 
Both are put aside at room temperature, to be examined after twenty- 
four to forty-eight hours. At the end of that time, the check plate 
is as clear as ever, the one which the fly has walked is dotted with 
colonies of bacteria and fungi. The value in the experiment consists 
in emphasizing that by this method we merely render visible what is 
constantly occurring in nature. 

A comparable experiment which we use in our elementary labora¬ 
tory work is to take three samples of clean (preferably, sterile) fresh 
milk in sterile bottles. One of them is plugged with a pledget of 
cotton, into the second is dropped a fly from the laboratory and into 
the third is dropped a fly which has been caught feeding upon gar¬ 
bage or other filth. After a minute or two the flies are removed and 
the vials plugged as was number one. The three are then set aside 
at room temperature. When examined after twenty-four hours 
the milk in the first vial is either still sweet or has a “ clean” sour odor; 
that of the remaining two is very different, for it has a putrid odor, 
which is usually more pronounced in the case of sample number 
three. 

Several workers have carried out experiments to determine the 
number of bacteria carried by flies under natural conditions. 'One 
of the most extended and best known of these is the series by Esten 
and Mason (1908). These workers caught flies from various sources 
in a sterilized net, placed them in a sterile bottle and poured over 
them a known quantity of sterilized water, in which they were shaken 
so as to wash the bacteria from their bodies. They found the number 
of bacteria on a single fly to range from 550 to 6,600,000. Early in 


152 


Arthropods as Simple Carriers of Disease 


the fly season the numbers of bacteria on flies are comparatively 
small, while later the numbers are comparatively very large. The 
place where flies live also determines largely the numbers that they 
carry. The lowest number, 550, was from a fly caught in the 
bacteriological laboratory, the highest number, 6,600,000 was the 
average from eighteen swill-barrel flies. Torrey (1912) made exami¬ 
nation of “wild” flies from a tenement house district of New York 
City. He Hound “that the surface contamination of these ‘wild’ 
flies may vary from 570 to 4,400,000 bacteria per insect, and the 
intestinal bacterial content from 16,000 to 28,000,000.” 

Less well known in this country is the work of Cox, Lewis, and 
Glynn (1912). They examined over four hundred and fifty naturally 
infected house-flies in Liverpool during September and early October. 
Instead of washing the flies they were allowed to swim on the surface 
of sterile water for five, fifteen, or thirty minutes, thus giving natural 
conditions, where infection occurs from vomit and dejecta of the 
flies, as well as from their bodies. They found, as might be expected, 
that flies from either insanitary or congested areas of the city contain 
far more bacteria than those from the more sanitary, less congested, 
or suburban areas. The number of aerobic bacteria from the former 
varied from 800,000 to 500,000,000 per fly and from the latter from 
21,000 to 100,000. The number of intestinal forms conveyed by 
flies from insanitary or congested areas was from 10,000 to 333,000,000 
as compared with from 100 to 10,000 carried by flies from the more 
sanitary areas. 

Pathogenic bacteria and those allied to the food poisoning group 
were only obtained from the congested or moderately congested 
areas and not from the suburban areas, where the chances of infesta¬ 
tion were less. 

The interesting fact was brought out that flies caught in milk 
shops apparently carry and obtain more bacteria than those from 
other shops with exposed food in a similar neighborhood. The 
writers explained this as probably due to the fact that milk when 
accessible, especially during the summer months, is suitable culture 
medium for bacteria, and the flies first inoculate the milk and later 
reinoculate themselves, and then more of the milk, so establishing a 
vicious circle. 

They conclude that in cities where food is plentiful flies rarely 
migrate from the locality in which they arc bred, and consequently 
the number of bacteria which they carry depends upon the general 


The House-fly as a Carrier of Disease 


i53 


standard of cleanliness in that locality. Flies caught in a street of 
modem, fairly high class, workmen’s dwellings forming a sanitary 
oasis in the midst of a slum area, carried far less bacteria than those 
caught in the adjacent neighborhood. 

Thus, as the amount of dirt carried by flies in any particular 
locality, measured in the terms of bacteria, bears a definite relation 
to the habits of the people and to the state of the streets, it demon¬ 
strates the necessity of efficient municipal and domestic cleanliness, 
if the food of the inhabitants is to escape pollution, not only with 
harmless but also with occasional pathogenic bacteria. 

The above cited w T ork is of a general nature, but, especially in 
recent years, many attempts have been made to determine more 
specifically the ability of flies to transmit pathogenic organisms. 
The critical reviews of Nuttall and Jepson (1909), Howard (1911), 
and Graham-Smith (1913) should be consulted by the student of 
the subject. We can only cite here a few of the more striking experi¬ 
ments. 

Celli (1888) fed flies on pure cultures of Bacillus typhosus and de¬ 
clared that he was able to recover these organisms from the intestinal 
contents and excrement. 

Firth and Horrocks (1902), cited by Nuttall and Jepson, “kept 
Musca domestica (also bluebottles) in a large box measuring 4x3x3 
feet, with one side made of glass. They were fed on material 
contaminated u r ith cultures of B. typhosus. Agar plates, litmus, 
glucose broth and a sheet of clean paper were at the same time 
exposed in the box. After a few days the plates and broth were 
removed and incubated with a positive result.” Graham-Smith 
(1910) “carried out experiments with large numbers of flies kept 
in gauze cages and fed for eight hours on emulsions of B. typhosus 
in syrup. After that time the infested syrup was removed and the 
flies were fed on plain syrup. B. typhosus was isolated up to 48 
horns (but not later) from emulsions of their feces and from plates 
over w r hich they walked.” 

Several other w r orkers, notably Hamilton (1903), Ficker (1903), 
Bertarelli (1910) Faichnie (1909), and Cochrane (1912), have iso¬ 
lated B. typhosus from “wild” flies, naturally infected. The papers 
of Faichnie and of Cochrane we have not seen, but they are quoted 
in extenso by Graham-Smith (1913). 

On the whole, the evidence is conclusive that typhoid germs not 
only may be accidentally carried on the bodies of house-flies but 


154 


Arthropods as Simple Carriers of Disease 


may pas's through their bodies and be scattered in a viable condition 
in the feces of the fly for at least two days after feeding. Similar, 
results have been reached in experiments with cholera, tuberculosis 
and yaws, the last-mentioned being a spirochaete disease. Darling 
(1913) has shown that murrina, a trypanosome disease of horses 
and mules in the Canal zone is transmitted by house-flies which feed 
upon excoriated patches of diseased animals and then pass to cuts 
and galls of healthy animals. 

Since it is clear that flies are abundantly able to disseminate 
viable pathogenic bacteria, it is important to consider whether they 
have access to such organisms in nature. A consideration of the 
method of spread of typhoid will serve to illustrate the way in which 
flies may play an important r 61 e. 

Typhoid fever is a specific disease caused by Bacillus typhosus , 
and by it alone. The causative organism is to be found in the excre¬ 
ment and urine of patients suffering from the disease. More than 
that, it is often present in the dejecta for days, weeks, or even months 
and years, after the individual has recovered from the disease. 
Individuals so infested are known as “typhoid carriers” and they, 
together with those suffering from mild cases, or “walking typhoid,” 
are a constant menace to the health of the community in which they 
are found. 

Human excrement is greedily visited by flies, both for feeding and 
for ovipositing. The discharges of typhoid patients, or of chronic 
“carriers,” when passed in the open, in box privies, or camp latrines, 
or the like, serve to contaminate myriads of the insects which may 
then spread the germ to human food and drink. Other intestinal 
diseases may be similarly spread. There is abundant epidsemiologi- 
cal evidence that infantile diarrhoea, dysentery, and cholera may be 
so spread. 

Stiles and Keister (1913) have shown that spores of Lamblia 
intestinalis, a flagellate protozoan living in the human intestine, 
may be carried by house-flies. Though this species is not normally 
pathogenic, one or more species of Entamoeba are the cause of a type 
of a highly fatal tropical dysentery. Concerning it, and another 
protozoan parasite of man, they say, “If flies can carry Lamblia 
spores measuring 10 to 7 [jl, and bacteria that arc much smaller, and 
particles of lime that arc much larger, there is no ground to assume 
that flies may not carry Entamoeba and Trichomonas spores. 



The House-fly as a Carrier of Disease 


155 


Tuberculosis is one of the diseases which it is quite conceivable 
may be carried occasionally. The spurirm of tubercular patients 
is very attractive to flies, and various workers, notably Graham- 
Smith, have found that Musca domestica may distribute the bacillus 
for several days after feeding on infected material. 

A type of purulent opthalmia which is very prevalent in Egypt 
is often said to be carried by flies. Nuttall and Jepson (1909) 
consider that the evidence regarding the spread of this disease by 
flies is conclusive and that the possibility of gonorrhoeal secretions 
being likewise conveyed cannot be denied. 

Many studies have been published, showing a marked agreement 
between the occurrence of typhoid and other intestinal diseases 
and the prevalence of house-flies. The most clear-cut of these are 
the studies of the Army Commission appointed to investigate the 
cause of epidemics of enteric fever in the volunteer camps in the 
Southern United States during the Spanish-American War. Though 
their findings as presented by Vaughan (1909), have been quoted 
very many times, they are so germane to our discussion that they 
will bear repetition: 

“Flies swarmed over infected fecal matter in the pits and fed 
upon the food prepared for the soldiers in the mess tents. In some 
instances where lime had recently been sprinkled over the contents 
of the pits, flies with their feet whitened with lime were seen walking 
over the food.” Under such conditions it is no wonder that “These 
pests had inflicted greater loss upon American soldiers than the arms 
of Spain.” 

Similar conditions prevailed in South Africa during the Boer War. 
Seamon believes that very much of the success of the Japanese in 
their fight against Russia was due to the rigid precautions taken to 
prevent the spread of disease by these insects and other means. 

Veeder has pointed out that the characteristics of a typical fly- 
borne epidemic of typhoid are that it occurs in little neighborhood 
epidemics, extending by short leaps from house to house, without 
regard to water supply or anything else in common. It tends to 
follow the direction of prevailing winds (cf. the conclusions of Hindle 
and Merriman). It occurs during warm weather. Of course, when 
the epidemic is once well under way, other factors enter into its spread. 

In general, flies may be said to be the chief agency in the spread of 
typhoid in villages and camps. In cities with modern sewer systems 
they are less important, though even under the best of such condi- 


156 Arthropods as Simple Carriers of Disease 

tions, they are important factors. Howard has emphasized that in 
such cities there are still many uncared-for box privies and that, in 
addition, the deposition of feces overnight in uncared-for waste lots 
and alleys is common. 

Not only unicellular organisms, such as bacteria and protozoa, 
but also the eggs, embryos and larvae of parasitic worms have been 
found to be transported by house-flies. Ransom (1911) has found 
that Habronema muscce, a nematode worm often found in adult flies, 
is the immature stage of a parasite occurring in the stomach of the 
horse. The eggs or embryos passing out with the feces of the horse, 
are taken up by fly larvae and carried over to the imago stage. 

Grassi (1883), Stiles (1889), Calandruccio (1906), and especially 
Nicoll (1911), have been the chief investigators of the ability of 
house-flies to carry the ova and embryos of human intestinal parasites. 
Graham-Smith (1913) summarizes the work along this line as follows: 

“It is evident from the investigations that have been quoted that 
house-flies and other species are greatly attracted to the ova of 
parasitic worms contained in feces and other materials, and make 
great efforts to ingest them. Unless the ova are too large they often 
succeed, and the eggs are deposited uninjured in their feces, in some 
cases up to the third day at least. The eggs may also be carried on 
their legs or bodies. Under suitable conditions, food and fluids 
may be contaminated with the eggs of various parasitic worms by flies, 
and in one case infection of the human subject has been observed. 
Feces containing tape-worm segments may continue to be a source of 
infection for as long as a fortnight. Up to the present, however, 
there is no evidence to show what part flies play in the dissemination 
of parasitic worms under natural conditions.” 

Enough has been said to show that the house-fly must be dealt 
with as a direct menace to public health. Control measures are 
not merely matters of convenience but are of vital importance. 

Under present conditions the speedy elimination of the house-fly 
is impossible and the first thing to be considered is methods of pro¬ 
tecting food and drink from contamination. The first of these 
methods is the thorough screening of doors and windows to prevent 
the entrance of flies. In the case of kitchen doors, the flies, attracted 
by odors, are likely to swarm onto the screen and improve the first 
opportunity for gaining an entrance. This difficulty can be largely 
avoided by screening-in the back porch and placing the screen door 
at one end rather than directly before the door. 



The House-fly as a Carrier of Disease # 157 

The use of sticky fly paper to catch the pests that gain entrance 
to the house is preferable to the various poisons o£ten used. Of the 
latter, formalin (40 per cent formaldehyde) in the proportion of two 
tablespoonfuls to a pint of water is very efficient, if all other liquids 
are removed or covered, so that the flies must depend on the formalin 
for drink. The mixture is said to be made more attractive by the 
addition of sugar or milk, though we have found the plain solution 
wholly satisfactory, under proper conditions. It should be em¬ 
phasized that this formalin mixture is not perfectly harmless, as so 
often stated. There are on record cases of severe and even fatal 
poisoning from the accidental drinking of solutions. 

When flies are very abundant in a room they can be most readily 
gotten rid of by fumigation with sulphur, or by the use of pure 
pyrethrum powder either burned or puffed into the air. Herrick 
(1913) recommends the following method: “At night all the doors 
and windows of the kitchen should be closed; fresh powder should 
be sprinkled over the stove, on the window ledges, tables, and in the 
air. In the morning flies will be found lying around dead or stupified. 
They may then be swept up and burned.” This method has proved 
very efficaceous in some of the large dining halls in Ithaca. 

The writers have had little success in fumigating with the vapors 
of carbolic acid, or carbolic acid and gum camphor, although these 
methods will aid in driving flies from a darkened room. 

All of these methods are but makeshifts. As Howard has so well 
put it, “the truest and simplest way of attacking the fly problem 
is to prevent them from breeding, by the treatment or abolition of 
all places in which they can breed. To permit them to breed un¬ 
disturbed and in countless numbers, and to devote all our energy to 
the problem of keeping them out of our dwellings, or to destroy them 
after they have once entered in spite of all obstacles, seems the 
wrong way to go about it.” 

We have already seen that Musca doniestica breeds in almost any 
fermenting organic material. While it prefers horse manure, it 
breeds also in human feces, cow dung and that of other animals, 
and in refuse of many kinds. To efficiently combat the insect, 
these breeding places must be removed or must be treated in some 
such way as to render them unsuitable for the development of the 
larvae. Under some conditions individual work may prove effective, 
but to be truly efficient there must be extensive and thorough co¬ 
operative efforts. 


158 Arthropods as Simple Carriers of Disease 

Manure, garbage, and the like should be stored in tight receptacles 
and carted away at least once a week. The manure may be carted 
to the fields and spread. Even in spread manure the larvae may con¬ 
tinue their development. Howard points out that “it often happens 
that after a lawn has been heavily manured in early summer the 
occupants of the house will be pestered with flies for a time, but 
finding no available breeding place these disappear sooner or later. 
Another generation will not breed in the spread manure.” 

Hutchinson (1914) has emphasized that the larvae of house¬ 
flies have deeply engrained the habit of migrating in the prepupal 
stage and has shown that this offers an important point of attack 
in attempts to control the pest. He has suggested that maggot 
traps might be developed into an efficient weapon in the warfare 
against the house-fly. Certain it is that the habit greatly simplifies the 
problem of treating the manure for the purpose of killing the larvae. 

There have been many attempts to find some cheap chemical 
which would destroy fly larvae in horse manure without injuring the 
bacteria or reducing the fertilizing values of the manure.. The litera¬ 
ture abounds in recommendations of kerosene, lime, chloride of lime, 
iron sulphate, and other substances, but none of them have met the 
situation. The whole question has been gone into thoroughly by 
Cook, Hutchinson and Scales (1914), who tested practically all of the 
substances which have been recommended. They find that by far 
the most effective, economical, and practical of the substances is 
borax in the commercial form in which it is available throughout the 
•country. 

“Borax increases the water-soluble nitrogen, ammonia and alkali¬ 
nity of manure and apparently does not permanently injure the 
bacterial flora. The application of manure treated with borax at the 
rate of 0.62 pound per eight bushels (10 cubic feet) to soil does not 
injure the plants thus far tested, although its cumulative effect, if 
.any, has not been determined.” 

As their results clearly show that the substances so often recom¬ 
mended are inferior to borax, we shall quote in detail their directions 
for treating manure so as to kill fly eggs and maggots. 

“Apply 0.62 pound borax or 0.75 pound calcined colemanite to 
•every 1 o cubic feet (8 bushels) of manure immediately on its removal 
from the barn. Apply the borax particularly around the outer 
edges of the pile with a flour sifter or any fine sieve, and sprinkle two 
■or three gallons of water over the borax-treated manure. 


The House-fly as a Carrier of Disease 


i59 


“The reason for applying the borax to the fresh manure immedi¬ 
ately after its removal from the stable is that the flies lay their eggs 
on the fresh manure, and borax, when it comes in contact with the 
eggs, prevents their hatching. As the maggots congregate at the 
outer edge of the pile, most of the borax should be applied there. 
The treatment should be repeated with each addition of fresh manure, 
but when the manure is kept in closed boxes, less frequent applica¬ 
tions will be sufficient. When the calcined colemanite is available, 
it may be used at the rate of 0.75 pound per 10 cubic feet of manure, 
and is a cheaper means of killing the maggots. In addition to the 
application of borax to horse manure to kill fly larvae, it may be 
applied in the same proportion to other manures, as well as to refuse 
and garbage. Borax may also be applied to the floors and crevices in 
bams, stables, markets, etc., as well as to street sweepings, and water 
should be added as in the treatment of horse manure. After estimat¬ 
ing the amount of material to be treated and weighing the necessary’ 
amount of borax, a measure may be used which will hold the proper 
amount, thus avoiding the subsequent weighings. 

“While it can be safely stated that no injurious action will follow 
the application of manure treated with borax at the rate of 0.62 
pound for eight bushels, or even larger amounts in the case of some 
plants, nevertheless the borax-treated manure has not been studied 
in connection with the growth of all crops, nor has its cumulative 
effect been determined. It is therefore recommended that not more 
than 15 tons per acre of the borax-treated manure should be applied 
to the field. As truckmen use considerably more than this amount, 
it is suggested that all cars containing borax-treated manure be so 
marked, and that public-health officials stipulate in their directions 
for this treatment that not over 0.62 pound for eight bushels of manure 
be used, as it has been shown that larger amounts of borax will 
injure most plants. It is also recommended that all public-health 
officials and others, in recommending the borax treatment for kill¬ 
ing fly eggs and maggots in manure, warn the public against the 
injurious effects of large amounts of borax on the growth of plants.” 

“The amount of manure from a horse varies with the straw or 
other bedding used, but 12 or 15 bushels per week represent the 
approximate amount obtained. As borax costs from five to six 
cents per pound in ioo-pound lots in Washington, it will make the 
cost of the borax practically one cent per horse, per day. And if 
calcined colemanite is purchased in large shipments the cost should 
be considerably less.” 


160 Arthropods as Simple Carriers of Disease 

Hodge (1910) has approached the problem of fly extermination 
from another viewpoint. He believes that it is practical to trap 
flies out of doors during the preoviposition period, when they are 
sexually immature, and to destroy such numbers of them that the 
comparatively few which survive will not be able to lay eggs in suffi- 
cent numbers to make the next generation a nuisance. To the end 
of capturing them in enormous numbers he has devised traps to be 
fitted over garbage cans, into stable windows, and connected with the 
kitchen window screens. Under some conditions this method of 
attack has proved very satisfactory. 

One of the most important measures for preventing the spread 
of disease by flies is the abolition of the common box privy. In 
villages and rural districts this is today almost the only type to be 
found. It is the chief factor in the spread of typhoid and other 
intestinal diseases, as well as intestinal parasites. Open and ex¬ 
posed to myriads of flies which not only breed there but which feed 
upon the excrement, they furnish ideal conditions for spreading con¬ 
tamination. Even where efforts are made to cover the contents 
with dust, or ashes, or lime, flies may continue to breed unchecked. 
Stiles and Gardner have shown that house-flies buried in a screened 
stand-pipe forty-eight inches under sterile sand came to the surface. 
Other flies of undetermined species struggled up through seventy- 
two inches of sand. 

So great is the menace of the ordinary box privy that a number of 
inexpensive and simple sanitary privies have been designed for use 
where there are not modem sewer systems. Stiles and Lumsden 
(1911) have given minute directions for the construction of one of the 
best types, and their bulletin should be obtained by those interested. 

Another precaution which is of fundamental importance in 
preventing the spread of typhoid, is that of disinfecting all discharges 
from patients suffering with the disease. For this purpose, quick¬ 
lime is the cheapest and is wholly satisfactory. In chamber vessels 
it should be used in a quantity equal to that of the discharge to be 
treated. It should be allowed to act for two hours. Air-slaked 
lime is of no value whatever. Chloride of lime, carbolic acid, or 
formalin may be used, but are more expensive. Other intestinal 
diseases demand similar precautions. 

Stomoxys calcitrans, the stable-fly— It is a popular belief that 
house-flies bite more viciously just before a rain. As a matter of 


Stomoxys calcitrans, the Stable-fly 


161 

fact, the true house-flies never bite, for their mouth-parts are not 
fitted for piercing. The basis of the misconception is the fact that a 
true biting fly, Stomoxys calcitrans (fig. no), closely resembling the 
house-fly, is frequently found in houses and may be driven in in 
greater numbers by muggy weather. From its usual habitat this 
fly is known as the “stable-fly” or, sometimes as the “biting house¬ 
fly.” 

Stomoxys calcitrans may be separated from the house-fly by the use 
of the key on p. 145. It may be more fully characterized as follows: 

The eyes of the male are separated by a distance equal to one- 
fourth of the diameter of the head, in the female by one-third. The 



110. Stomoxys calcitrans; adult, larva, puparium and details. (x5). After Howard. 


frontal stripe is black, the cheeks and margins of the orbits silvery- 
white. The antennae are black, the arista feathered on the upper 
side only. The proboscis is black, slender, fitted for piercing and 
projects forward in front of the head. The thorax is grayish, marked 
by four conspicuous, more or less complete black longitudinal stripes; 
the scutellum is paler; the macrochaetas are black. The abdomen is 
gray, dorsally with three brown spots on the second and third seg¬ 
ments and a median spot on the fourth. These spots are more 
pronounced in the female. The legs are black, the pulvilli distinct. 
The wings are hyaline, the vein Mi + 2 less sharply curved than in 
the house-fly, the apical cell being thus more widely open (cf. fig. 
no). Length 7 mm. 

This fly is widely distributed, being found the world over. It was 
probably introduced into the United States, but has spread to all 




162 


Arthropods as Simple Carriers of Disease 


parts of the country. Bishopp (1913) regards it as of much more 
importance as a pest of domestic animals in the grain belt than else¬ 
where in the United States. The life-history and habits of this 
species have assumed a new significance since it has been suggested 
that it may transmit the human diseases, infantile paralysis and 
pellagra. In this country, the most detailed study of the fly is that 
of Bishopp (1913) whose data regarding the life cycle are as follows: 

The eggs like those of the house-fly, are about one mm. 
in length. Under a magnifying glass they show a distinct furrow 
along one side. When placed on any moist substance they hatch 
in from one to three days after being deposited. 

The larvae or maggots (fig. 110) have the typical shape and actions 
of most maggots of the Museid group. They can be distinguished 
from those of the house-fly as the stigma-plates are smaller, much 
further apart, with the slits less sinuous. Development takes place 
fairly rapidly when the proper food conditions are available and 
the growth is completed within eleven to thirty or more days. 

The pupa (fig. no), like that of related flies, undergoes its develop¬ 
ment within the contracted and hardened last larval skin, or pu- 
parium. This is elongate oval, slightly thicker towards the head end, 
and one-sixth to one-fourth of an inch in length. The pupal stage 
requires six to twenty days, or in cool weather considerably longer. 

The life-cycle of the stable-fly is therefore considerably longer 
than that of Musca domestica. Bishopp found that complete 
development might be undergone in nineteen days, but that the 
average period was somewhat longer, ranging from twenty-one to 
twenty-five days, where conditions are very favorable. The longest 
period which he observed was forty-three days, though his finding 
of full grown larvae and pupae in straw during the latter part of 
March, in Northern Texas, showed that development may require 
about three months, as he considered that these stages almost cer¬ 
tainly developed from eggs deposited the previous December. 

The favorite breeding place, where available, seems to be straw or 
manure mixed with straw. It also breeds in great numbers in horse- 
manure, in company with Musca domestica. 

Ncwstead considers that in England the stable-fly hibernates in 
the pupal stage. Bishopp finds that in the southern part of the 
United States there is no true hibernation, as the adults have been 
found to emerge at various times during the winter. He believes 
that in the northern United States the winter is normally passed 


Other Arthropods as Simple Carriers 


163 


in the larval and pupal stages, and that the adults which have been 
observed in heated stables in the dead of winter were bred out in 
refuse within the warm bams and were not hibernating adults. 

Graham-Smith (1913) states that although the stable-fly fre¬ 
quents stable manure, it is probably not an important agent in 
distributing the organisms of intestinal diseases. Bishopp makes the 
important observation that “it has never been found breeding in 
human excrement and does not frequent malodorous places, which 
are so attractive to the house-fly. Hence it is much less likely to 
carry typhoid and other germs which may be found in such places.” 

Questions of the possible agency of Stomoxys calcitrans in the trans¬ 
mission of infantile paralysis and of pellagra, we shall consider later. 

Other arthropods which may serve as simple carriers of patho¬ 
genic organisms —It should be again emphasized that any insect which 
has access to, and comes in contact with, pathogenic organisms 
and then passes to the food, or drink, or the body of man, may serve 
as a simple carrier of disease. In addition to the more obvious 
illustrations, an interesting one is the previously cited case of the 
transfer of Dermatobia cyaniventris by a mosquito (fig. 81-84). 
Darling (1913) has shown that in the tropics, the omnipresent ants 
may be important factors in the spread of disease. 


CHAPTER VI 


ARTHROPODS AS DIRECT INOCULATORS OF DISEASE GERMS 

We have seen that any insect which, like the house-fly, has access 
to disease germs and then comes into contact with the food or drink 
of man, may serve to disseminate disease. Moreover, it has been 
clearly established that a contaminated insect, alighting upon 
wounded or abraded surfaces, may infect them. These are instances 
of mere accidental, mechanical transfer of pathogenic organisms. 

Closely related are the instances of direct inoculation of disease 
germs by insects and other arthropods. In this type, a blood¬ 
sucking species not only takes up the germs but, passing to a healthy 
individual, it inserts its contaminated mouth-parts and thus directly 
inoculates its victim. In other words, the disease is transferred 
just as blood poisoning may be induced by the prick of a contami¬ 
nated needle, or as the laboratory worker may inoculate an experi¬ 
mental animal. 

Formerly, it was supposed that this method of the transfer of 
disease by arthropods was a very common one and many instances 
are cited in the earlier literature of the subject. It is, however, 
difficult to draw a sharp line between such cases and those in which, 
on the one hand, the arthropod serves as a mere passive carrier or, 
on the other hand, serves as an essential host of the pathogenic 
organism. More critical study of the subject has led to the belief 
that the importance of the role of arthropods as direct inoculators 
has been much overestimated. 

The principal reason for regarding this phase of the subject as 
relatively unimportant, is derived from a study of the habits of the 
blood-sucking species. It is found that, in general, they are inter¬ 
mittent feeders, visiting their hosts at intervals and then abstaining 
from feeding for a more or less extended period, while digesting their 
meal. In the meantime, most species of bacteria or of protozoan 
parasites with which they might have contaminated their mouth- 
parts, would have perished, through inability to withstand drying. 

In spite of this, it must be recognized that this method of transfer 
does occur and must be reckoned with in any consideration of the 
relations of insects to disease. We shall first cite some general 
illustrations and shall then discuss the role of fleas in the spreading 
of bubonic plague, an illustration which cannot be regarded as typi¬ 
cal, since it involves more than mere passive carnage. 


Some Illustrations of Direct Inoculation 165 

Some Illustrations of Direct Inoculation of Disease Germs 

by Arthropods 

In discussing poisonous arthropods, we have already emphasized 
that species which are of themselves innocuous to man, may occasion¬ 
ally introduce bacteria by their bite or sting and thus cause more or 
less severe secondary symptoms. That such cases should occur, is 
no more than is to be expected. The mouth-parts or the sting of 
the insect are not sterile and the chances of their carrying pyogenic 
organisms are always present. 

More strictly falling in the category of transmission of disease 
germs by direct inoculation are the instances where the insect, or 
related form, feeds upon a diseased animal and passes promptly to a 
healthy individual which it infects. Of such a nature are the follow¬ 
ing: 

Various species of biting flies are factors in the dissemination of 
anthrax, an infectious and usually fatal disease of animals and, 
occasionally, of man. That the bacteria with which the blood of 
diseased animals teem shortly before death might be transmitted 
by such insects has long been contended, but the evidence in support 
of the view has been unsatisfactory. Recently, Mitzmain (1914) 
has reported a series of experiments which show conclusively that the 
disease may be so conveyed by a horse-fly, Tabanus striatus, and by 
the stable-fly, Stomoxys calcitrans. 

Mitzmain’s experiments were tried with an artificially infected 
guinea pig, which died of the disease upon the third day. The flies 
were applied two and one-half hours, to a few minutes, before the 
death of the animal. With both species the infection was success¬ 
fully transferred to healthy guinea pigs by the direct method, in 
which the flies were interrupted while feeding on the sick animal. 
The evidence at hand does not warrant the conclusion that insect 
transmission is the rule in the case of this disease. 

The nagana, or tsetse-fly disease of cattle is the most virulent 
disease of domestic animals in certain parts of Africa. It is caused 
by a protozoan blood parasite, Trypanosoma brucei, which is con¬ 
veyed to healthy animals by the bite of Glossina morsitans and possi¬ 
bly other species of tsetse-flies. The flies remain infective for 
forty-eight hours after feeding on a diseased animal. The insect 
also serves as an essential host of the parasite. 

Surra, a similar trypanosomiasis affecting especially horses and 
mules, occurs in southern Asia, Malaysia, and the Philippines where 


166 Arthropods as Direct Inoculators of Disease Germs 

the tsetse-flies are not to be found. It is thought to be spread by 
various species of blood-sucking flies belonging to the genera Stomoxys, 
Hcematobia, and Tabanus. Mitzmain (1913) demonstrated that in 
the Philippines it is conveyed mechanically by Tabanus striatus. 

The sleeping sickness of man, in Africa, has also been supposed 
to be directly inoculated by one, or several, species of tsetse-flies. 
It is now known that the fly may convey the disease for a short 
time after feeding, but that there is then a latent period of from 
fourteen to twenty-one days, after which it again becomes infectious. 
This indicates that in the meantime the parasite has been under¬ 
going some phase of its life-cycle and that the fly serves as an inter¬ 
mediate host. We shall therefore consider it more fully under that 
grouping. 

These are a few of the cases of direct inoculation which may be 
cited as of the simpler type. We shall next consider the rdle of the 
flea in the dissemination of the bubonic plague, an illustration 
complicated by the fact that the bacillus multiples within the insect 
and may be indirectly inoculated. 

The Role of Fleas in the Transmission of the Plague 

The plague is a specific infectious disease caused by Bacillus pestis. 
It occurs in several forms, of which the bubonic and the pneumonic 
are the most common. According to Wyman, 80 per cent of the 
human cases are of the bubonic type. It is a disease which, under 
the name of oriental plague, the pest, or the black death, has ravaged 
almost from time immemorial the countries of Africa, Asia, and 
Europe. The record of its ravages are almost beyond belief. In 542 
A. D. it caused in one day ten thousand deaths in Constantinople. 
In the 14th century it was introduced from the East and prevailed 
throughout Armenia, Asia Minor, Egypt and Northern Africa and 
Europe. Hecker estimates that one-fourth of the population of 
Europe, or twenty-five million persons, died in the epidemic of that 
century. From then until the 17th century it was almost constantly 
present in Europe, the great plague of London, in 1665 killing 68,596 
out of a population of 460,000. Such an epidemic would mean for 
New York City a proportionate loss of over 600,000 in a single year. 
It is little wonder that in the face of such an appalling disaster sus¬ 
picion and credulity were rife and the wildest demoralization ensued. 

During the 14th century the Jews were regarded as responsible 
for the disease, through poisoning wells, and were subjected to the 


Role of Fleas in the Transmission of Plague 



111. A contemporaneous engraving of the pest hospital in Vienna in 1679 . 

After Peters. 

most incredible persecution and torture. In Milan the visitation 
of 1630 was credited to the so-called anointers, — men who were 
supposed to spread the plague by anointing the walls with magic 
ointment — and the most horrible tortures that human ingenuity 
could devise were imposed on scores of victims, regardless of rank 
or of public service (fig. ii2,a). Manzoni’s great historical novel, 
“The Betrothed” has well pictured conditions in Italy during this 
period. 

In modem times the plague is confined primarily to warm climates, 
a condition which has been brought about largely through general 
improvement in sanitary conditions. 

At present, the hotbed of the disease is India, where there were 
1,040,429 deaths in 1904 and where in a period of fifteen years, 
ending with January 1912, there were over 15,000,000 deaths. The 
reported deaths in that country for 1913 totaled 198,875. 

During the winter of 1910-11 there occurred in Manchuria and 
North China a virulent epidemic of the pneumonic plague which 
caused the death of nearly 50,000 people. The question as to its 
origin and means of spread will be especially referred to later. 

Until recent years, the plague had not been known to occur in 
the New World but there were outbreaks in Brazil and Hawaii in 
1899, and in 1900 there occurred the first cases in San Francisco. 











i68 


Arthropods as Direct Inoculators of Disease Germs 



112 a. A medieval method of combating the plague. The persecution of the anointers in Milan in 1630 . From 
copy of “II processi originale degli untori“ in the library of Cornell University. 




























Role of Fleas in the Transmission of Plague 169 

In California there were 125 cases in the period 1900-04; three cases 
in the next three years and then from May 1907 to March 1908, 
during the height of the outbreak, 170 cases. Since that time there 
have been only sporadic cases, the last case reported being in May 
1914. Still more recent were the outbreaks in the Philippine Islands, 
Porto Rico, and Cuba. 

On June 24, 1914, there was recognized a case of human plague 
in New Orleans. The Federal Health Service immediately took 
charge, and measures for the eradication of the disease were vigor¬ 
ously enforced. Up to Otcober 10, 1914 there had been reported 
30 cases of the disease in man, and 18 r cases of plague in rats. 



112 b. The modern method of combating the plague. A day's catch of rats in the fight 
against plague in San Francisco. Courtesy of Review of Reviews. 


The present-day methods of combating bubonic plague are well 
illustrated by the fight in San Francisco. Had it not been for the 
strenuous and radical anti-plague campaign directed by the United 
States Marine Hospital Service we might have had in our own 
country an illustration of what the disease can accomplish. On what 
newly acquired knowledge was this fight based? 

The basis was laid in 1894, when the plague bacillus was first 
discovered. All through the centuries, before and during the Christian 
era, down to 1894, the subject was enveloped in darkness and there 
had been a helpless, almost hopeless struggle in ignorance on the part 
of physicians, sanitarians, and public health officials against the 
ravages of this dread disease, Now its cause, method of propaga¬ 
tion and means to prevent its spread are matters of scientific cer¬ 
tainty. 









170 Arthropods as Direct Inoculators of Disease Germs 

After the discovery of the causative organism, one of the first 
advances was the establishment of the identity of human plague 
and that of rodents. It had often been noted that epidemics of the 
human disease were preceded by great epizootics among rats and 
mice. So well established was this fact that with the Chinese, 
unusual mortality among these rodents was regarded as foretelling 
a visitation of the human disease. That there was more than an 
accidental connection between the two was obvious when Yersin, 
the discoverer of Bacillus pestis, announced that during an epidemic 
the rats found dead in the houses and in the streets almost always 
contain the bacillus in great abundance in their organs, and that many 
of them exhibit veritable buboes. 

Once it was established that the diseases were identical, the atten¬ 
tion of the investigators was directed to a study of the relations 
between that of rats and of humans, and evidence accumulated to 
show that the bubonic plague was primarily a disease of rodents 
and that in some manner it was conveyed from them to man. 

There yet remained unexplained the method of transfer from rat 
to man. As long ago as the 16th century, Mercuralis suggested 
that house-flies were guilty of disseminating the plague but modem 
investigation, while blaming the fly for much in the way of spreading 
disease, show that it is an insignificant factor in this case. 

Search for blood-sucking insects which would feed on both rodents 
and man, and which might therefore be implicated, indicated that 
the fleas most nearly met the conditions. At first it was urged that 
rat fleas would not feed upon man and that the fleas ordinarily attack¬ 
ing man would not feed upon rats. More critical study of the habits 
of fleas soon showed that these objections were not well-founded. 
Especially important was the evidence that soon after the death of 
their host, rat fleas deserted its body and might then become a pest 
in houses "where they had not been noticed before. 

Attention was directed to the fact that while feeding, fleas are in 
the habit of squirting blood from the anus and that in the case of those 
which had fed upon rats and mice dying of the plague, virulent plague 
bacilli were to be found in such blood. Liston (1905) even found,, 
and subsequent investigations confirmed, that the jflague bacilli 
multiply in the stomach of the insect and that thus the blood ejected 
was richer in the organisms than was that of the diseased animal. 
It was found that a film of this infected blood spread out under the 
body of the flea and that thus the bacilli might be inoculated by the 
bite of the insect and by scratching. 




Role of Fleas in the Transmission of Plague 171 

Very recently, Bacot and Martin (1914) have paid especial 
attention to the question of the mechanism of the transmission of 
the plague bacilli by fleas. They believe that plague infested fleas 
regurgitate blood through tlje mouth, and that under conditions 
precluding the possibility of infection by dejecta, the disease may be 
thus transmitted. The evidence does not seem sufficient to establish 
that this is the chief method of transmission. 

Conclusive experimental proof that fleas transmit the disease is 
further available from a number of sources. The most extensive 
series of experiments is that of the English Plague Commission in 
India, which reported in 1906 that: 

On thirty occasions a healthy rat contracted plague in sequence 
of living in the neighborhood of a plague infected rat under cir¬ 
cumstances which prevented the healthy rat coming in contact with 
either the body or excreta of the diseased animal. 

In twenty-one experiments out of thirty-eight, healthy rats living 
in flea-proof cages contracted plague when exposed to rat fleas 
(.Xenopsylla cheopis ), collected from rats dead or dying of septicaemic 
plague. 

Close contact of plague-infected with healthy animals, if fleas 
are excluded, does not give rise to an epizootic among the latter. 
As the huts were never cleaned out, close contact included contact 
with feces and urine of infected animals, and contact with, and eat¬ 
ing of food contaminated with feces and urine of infected animals, 
as well as pus from open plague ulcers. Close contact of young, 
even when suckled by plague-infected mothers, did not give the 
disease to the former. 

If fleas are present, then the epizootic, once started, spreads from 
animal to animal, the rate of progress being in direct proportion to 
the number of fleas. 

Aerial infection was excluded. Thus guinea-pigs suspended in a 
cage two feet above the ground did not contract the disease, while 
in the same hut those animals allowed to run about and those placed 
two inches above the floor became infected. It had previously 
been found that a rat flea could not hop farther than about five 
inches. 

Guinea pigs and monkeys were placed in plague houses in pairs, 
both protected from soil contact infection and both equally exposed 
to aerial infection, but one surrounded with a layer of tangle-foot 
paper and the other surrounded with a layer of sand. The follow¬ 
ing observations were made: 


172 Arthropods as Direct Inoculators of Disease Germs 

(a) Many fleas were caught in the tangle-foot, a certain pro¬ 
portion of which were found on dissection to contain in their stomachs 
abundant bacilli microscopically identical with plague bacilli. Out 
of eighty-five human fleas dissected only one contained these bacilli, 
while out of seventy-seven rat fleas twenty-three were found thus 
infected. 

' ( b ) The animals surrounded with tangle-foot in no instance 
developed plague, while several (24 per cent) of the non-protected 
animals died of the disease. 

Thus, the experimental evidence that fleas transmit the plague 
from rat to rat, from rats to guinea pigs, and from rats to monkeys 
is indisputable. There is lacking direct experimental proof of its 
transfer from rodents to man but the whole chain of indirect evi¬ 
dence is so complete that there can be no doubt that such a transfer 
does occur so commonly that in the case of bubonic plague it must 
be regarded as the normal method. 

Rats are not the only animals naturally attacked by the plague 
but as already suggested, it occurs in various other rodents. In 
California the disease has spread from rats to ground squirrels 
(Otospermophilus beecheyi), a condition readily arising from the 
frequency of association of rats with the squirrels in the neighbor¬ 
hood of towns, and from the fact that the two species of fleas found 
on them are also found on rats. While the danger of the disease 
being conveyed from squirrels to man is comparatively slight, the 
menace in the situation is that the squirrels may become a more or 
less permanent reservoir of the disease and infect rats, which may 
come into more frequent contact with man. 

The tarbagan (Arctomys bobac ), is a rodent found in North Man¬ 
churia, which is much prized for its fur. It is claimed that this ani¬ 
mal is extremely susceptible to the plague and there is evidence to 
indicate that it was the primary source of the great outbreak of 
pneumonic plague which occurred in Manchuria and North China 
during the winter of 1910-11. 

Of fleas, any species which attacks both rodents and man may be 
an agent in the transmission of the plague. We have seen that in 
India the species most commonly implicated is the rat flea, Xenopsylla 
cheopis, (= Leemopsylla or Pulex cheopis) (fig. 89). This species has 
also been found commonly on rats in San Francisco. The cat flea, 
Ctenocephalus felis, the dog flea, Ctenocephalus cards, the human flea, 
Pulex irritans, the rat fleas, Ceratophyllus fasciatus and Ctenopsyllus 
musculi have all been shown to meet the conditions. 



Role of Fleas in the Transmission of Plague 173 

But, however clear the evidence that fleas are the most important 
agent in the transfer of plague, it is a mistake fraught with danger 
to assume that they are the only factor in the spread of the disease. 
The causative organism is a bacillus and is not dependent upon any 
insect for the completion of its development. 

Therefore, any blood-sucking insect which feeds upon a plague 
infected man or animal and then passes to a healthy individual, 
conceivably might transfer the bacilli. Verjbitski (1908) has shown 
experimentally that bed-bugs may thus convey the disease. Hertzog 
found the bacilli in a head-louse, Pediculus humanus, taken from a 
child which had died from the plague, and McCoy found them in a 
louse taken from a plague-infected squirrel. On account of their 
stationary habits, the latter insects could be of little significance in 
spreading the disease. 

Contaminated food may also be a source of danger. While this 
source, formerly supposed to be the principal one, is now regarded as 
unimportant, there is abundant experimental evidence to show that 
it cannot be disregarded. It is believed that infection in this way 
can occur only when there is some lesion in the alimentary canal. 

Still more important is the proof that in pneumonic plague the 
patient is directly infective and that the disease is spread from man 
to man without any intermediary. Especially conclusive is the 
evidence obtained by Drs. Strong and Teague during the Manchurian 
epidemic of 1910-11. They found that during coughing, in pneu¬ 
monic plague cases, even when sputum visible to the naked eye is 
not expelled, plague bacilli in large numbers may become widely 
disseminated into the surrounding air. By exposing sterile plates 
before patients who coughed a single time, very numerous colonies 
of the baccilus were obtained. 

But the great advance which has been made rests on the dis¬ 
covery that bubonic plague is in the vast majority of cases transmitted 
by the flea. The pneumonic type forms a very small percentage 
of the human cases and even with it, the evidence indicates that the 
original infection is derived from a rodent through the intermediary 
of the insect. 

So modem prophylactic measures are directed primarily against 
the rat and fleas. Ships coming from infected ports are no longer 
disinfected for the purpose of killing the plague germs, but are fumi¬ 
gated to destroy the rats and the fleas which they might harbor. 
When anchored at infected ports, ships must observe strenuous 


174 Arthropods as Direct Inoculators of Disease Germs 

precautions to prevent the ingress of rats. Cargo must be inspected 
just before being brought on board, in order to insure its freedom from 
rats. Even lines and hawsers must be protected by large metal discs 
or funnels, for rats readily run along a rope to reach the ship. Once 
infested, the ship must be thoroughly fumigated, not only to avoid 
carrying the disease to other ports but to obviate an outbreak on 
board. 

When an epidemic begins, rats must be destroyed by trapping 
and poisoning. Various so-called biological poisons have not proved 
practicable. Sources of food supply should be cut off by thorough 
cleaning up, by use of rat-proof garbage cans and similar measures. 
Hand in hand with these, must go the destruction of breeding places, 
and the rat-proofing of dwellings, stables, markets, warehouses, docks 
and sewers. All these measures are expensive, and a few years ago 
would have been thought wholly impossible to put into practice 
but now they are being enforced on a large scale in every fight against 
the disease. 

Rats and other rodents are regularly caught in the danger zone 
and examined for evidence of infection, for the sequence of the epi¬ 
zootic and of the human disease is now understood. In London, rats 
are regularly trapped and poisoned in the vicinity of the principal 
docks, to guard against the introduction of infected animals in ship¬ 
ping. During the past six years infected rats have been found 
yearly, thirteen having been found in 1912. In Seattle, Washington, 
seven infected rats were found along the water front in October, 1913, 
and infected ground squirrels are still being found in connection with 
the anti-plague measures in California, 

The procedure during an outbreak of the human plague was well 
illustrated by the fight in San Francisco. The city was districted, 
and captured rats, after being dipped in some fluid to destroy the fleas, 
were carefully tagged to indicate their source, and were sent to the 
laboratory for examination. If an infected rat was found, the officers 
in charge of the work in the district involved were immediately 
notified by telephone, and the infected building was subjected to a 
thorough fumigation. In addition, special attention was given to 
all the territory in the four contiguous blocks. 

By measures such as these, this dread scourge of the human race 
is being brought under control. Incidentally, the enormous losses 
due to the direct ravages of rats are being obviated and this alone 
would justify the expenditure many times over of the money and 
labor involved in the anti-rat measures. 



CHAPTER VII 


ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC ORGANISMS 

We now have to consider the cases in which the arthropod acts 
as the essential host of a pathogenic organism. In other words, 
cases in which the organism, instead of being passively carried or 
merely accidentally inoculated by the bite of its carrier, or vector , is 
taken up and undergoes an essential part of its development within 
the arthropod. 

In some cases, the sexual cycle of the parasite is undergone in the 
arthropod, which then serves as the definitive or 
primary host. In other cases, it is the asexual stage 
of the parasite which is undergone, and the arthropod 
then acts as the intermediate host. This distinction 
is often overlooked and all the cases incorrectly 
referred to as those in which the insect or other 
arthropod acts as intermediate host. 

We have already emphasized that this is the most 
important way in which insects may transmit disease, 
for without them the particular organisms concerned 
could never complete their development. Exter¬ 
minate the arthropod host and the life cycle of the 
parasite is broken, the disease is exterminated. 

As the phenomenon of alternation of generations, 
as exhibited by many of the parasitic protozoa, is a 
complicated one and usually new to the student, we 
shall first take up some of the grosser cases illustrated 

113. Dipylidium . . . . . 

caninum. The by certain parasitic worms. There is the additional 

double pored 

tapeworm of the reason that these were the first cases known of arthro- 

dog. . . . . 

pod transmission of pathogenic organisms. 

Insects as Intermediate Hosts of Tapeworms 

A number of tapev r orms are known to undergo their sexual stage 
in an insect or other arthropod. Of these at least tv r o are occasional 
parasites of man. 

Dipylidium caninum (figs. 113 and 114), more generally knovm as 
Taenia cucumerina or T. elliptica, is the commonest intestinal parasite 
of pet dogs and cats. It is occasionally found as a human parasite, 
70 per cent of the cases reported being in young children. 



175 


176 Arthropods as Essential Hosts of Pathogenic Organisms 



114. Dipylidium caninum. 
Rostrum evaginated and 
invaginated. After 
Blanchard. 


In 1869, Melnikoff found in a dog louse, Trichodectes canis, some 
peculiar bodies which Leuckart identified as the larval form of this 
tapeworm. The worm is, however, much more 
common in dogs and cats than is the skin para¬ 
site, and hence it appears that the Trichodectes 
could not be the only intermediate host. In 
1888, Grassi found that it could also develop 
in the cat and dog fleas, Ctenocephalus felis 
and C. canis , and in the human flea, Pulex 
irritans. 

The eggs, scattered among the hairs of the 
dog or cat, are ingested by the insect host and 
in its body cavity they develop into pyriform 
bodies, about 300(4. in length, almost entirely destitute of a bladder, 
but in the immature stage provided with a caudal appendage (fig. 115). 
Within the pear-shaped body (fig. 116) are the invaginated head and 
suckers of the future tapeworm. This larval 
form is known as a cysticercoid, in contradis¬ 
tinction to the bladder-like cysticercus of many 
other cestodes. It is often referred to in liter¬ 
ature as Cryptocystis trichodectis Villot. 

As many as fifty of the cysticercoids have 
been found in the body cavity of a single flea. 

When the dog takes up an infested flea or louse, 
by biting itself, or when the cat licks them up, the 
larvae quickly develop into tapeworms, reaching sexual maturity in 
about twenty days in the intestine of their host. Puppies and 
kittens are quickly infested when suckling a flea-infested mother, the 
developing worms having been found in the intestines of puppies not 
more than five or six days old. 

Infestation of human beings occurs only 
through accidental ingestion of an infested flea. 
It is natural that such cases should occur largely 
in children, where they may come about in 
some such way as illustrated in the accompany¬ 
ing figures 117 and 118. 

Hymenolepis diminuta, very commonly living in the intestine 
of mice and rats, is also known to occur in man. Its cysticercoid 
develops in the body cavity of a surprising range of meal-infesting 
insects. Grassi and Rovelli (abstract in Ransom, 1904) found it in the 



115. Dipylidium caninum. 
Immature cysticercoid. 
After Grassi and Rovelli. 



110 . 


Dipylidium caninum. 
Cysticercoid. After 
Villet. 





Insects as Intermediate Hosts of Tapeworms 


177 


larvae and adult of a moth, Asopia farinalis, m the earwig, Anisolabis 
annulipes, the Tenebrionid beetles Akis spinosa and Scaurus striatus. 



117. One way in which Dipylidium infection in 
children may occur. After Blanchard. 


Grassi considers that the lepi- 
dopter is the normal inter¬ 
mediate host. The insect takes 
up the eggs scattered by rats 
and mice. It has been experi¬ 
mentally demonstrated that 
man may develop the tape¬ 
worm by swallowing infested 
insects. Natural infection 
probably occurs by ingesting 
such insects with cereals, or 


imperfectly cooked foods. 

Hymenolepis lanceolata, a parasite of geese and ducks, has been 
reported once for man. The supposed cysticercoid occurs in various 
small crustaceans of the family Cyelopidae. 



118 . The probable method by which Dipylidium infection usually occurs. 






178 Arthropods as Essential Hosts of Pathogenic Organisms 

Several other cestode parasites of domestic animals are believed 
to develop their intermediate stage in certain arthropods. Among 
these may be mentioned: 

Choanotcenia infundibulformis,oi chickens, developing in the house¬ 
fly (Grassi and Rovelli); 

Davainea cesticilhis, of chickens, in some lepidopter or coleopter 
(Grassi and Rovelli); 

Hymenolepis anatina, H. gracilis, H. sinuosa, H. coronula and 
Fimbriaria fasciolaris, all occurring in ducks, have been reported as 
developing in small aquatic crustaceans. In these cases, cysticer- 
coids have been found which, on account of superficial characters, 
have been regarded as belonging to the several species, but direct 
experimental evidence is scant. 

Arthropods as Intermediate Hosts of Nematode Worms 

Filariasis and Mosquitoes— A number of species of Nematode 
worms belonging to the genus Filaria, infest man and other verte¬ 
brates and in the larval condition are to be found in the blood. 
Such infestation is known as filariasis. The sexually mature worms 
are to be found in the blood, the lymphatics, the mesentery and sub¬ 
cutaneous connective tissue. In the cases best studied it has been 
found that the larval forms are taken up by mosquitoes and undergo 
a transformation before they can attain maturity in man. 

The larva; circulating in the blood are conveniently designated 
as microfilariae. In this stage they are harmless and only one species, 
Filaria bancrofti, appears to be of any great pathological significance 
at any stage. 

Filaria bancrofti in its adult state, lives in the lymphatics of man. 
Though often causing no injury it has been clearly established that 
they and their eggs may cause various disorders due to stoppage 
of the lymphatic trunks (fig. 119). Manson lists among other effects, 
abscess, varicose groin glands, lymph scrotum, chyluria, and ele¬ 
phantiasis. 

The geographical distribution of this parasite is usually given as 
coextensive with that of elephantiasis, but it is by no means certain 
that it is the only cause of this disease and so actual findings of the 
parasites arc necessary. Manson reports that it is “an indigenous 
parasite in almost every country throughout the tropical and sub¬ 
tropical world, as far north as Spain in Europe and Charlestown in 



Filariasis and Mosquitoes 


179 


the United States, and as far south as Brisbane in Australia.” In 
some sections, fully 50 per cent of the natives are infested. Labredo 
(1910) found 17.82 per cent infestation in Havana. 

The larval forms of Filaria bancrofti were first discovered in 1863, 
by Demarquay, in a case of chylous dropsy. They were subse¬ 
quently noted under similar conditions, by several workers, and by 
Wiicherer in the urine of twenty-eight cases of tropical chyluria, 
but in 1872 Lewis found that the blood of man was the normal 
habitat, and gave them the name Filaria sanguinis hominis. The 

adult worm was found in 1876 
by Bancroft, and in 1877, 
Cobboldgave it the name Filaria 
bancrofti. It has since been 
found repeatedly in various parts 
of the lymphatic system, and its 
life-history has been the subject 
of detailed studies by Manson 
(1884), Bancroft (1899), Low 
(1900), Grassi and Noe (1900), 
Noe (1901) and Fullebom (1910). 

The larvae, as they exist in 
the circulating blood, exhibit a 
very active wriggling movement, 
without material progression. 
They may exist in enormous 
numbers, as many as five or 
six hundred swarming in a 
single drop of blood. This is the more surprising when we con¬ 
sider that they measure about 300;./. x 8(jl, that is, their width is 
equal to the diameter of the red blood corpuscle of their host and 
their length over thirty-seven times as great. 

Their organs are very immature and the structure obscure. When 
they have quieted down somewhat in a preparation it may be seen 
that at the head end there is a six-lipped and very delicate prepuce, 
enclosing a short “fang” which may be suddenly exserted and 
retracted. Completely enclosing the larva is a delicate sheath, 
which is considerably longer than the worm itself. To enter into 
further details of anatomy is beyond the scope of this discussion 
and readers interested are referred to the work of Manson and of 
Fullebom. 



119. Elephantiasis in Man. From “New 
Sydenham Society’s Atlas.” 






180 Arthropods as Essential Hosts of Pathogenic Organisms 

One of the most surprising features of the habits of these larvae 
is the periodicity which they exhibit in their occurrence in the peri¬ 
pheral blood. If a preparation be made during the day time there 
may be no evidence whatever of filarial infestation, whereas a prep¬ 
aration from the same patient taken late in the evening or during 
the night may be literally swarming with the parasites. Manson 
quotes Mackenzie as having brought out the further interesting 
fact that should a “filarial subject be made to sleep during the day 
and remain awake at night, the periodicity is reversed; that is to say, 
the parasites come into the blood during the day and disappear from 
it during the night.” There have been numerous attempts to explain 
this peculiar phenomenon of periodicity but in spite of objections 
which have been raised, the most plausible remains that of Manson, 
who believes that it is an adaptation correlated with the life-habits 
of the liberating agent of the parasite, the mosquito. 

The next stages in the development of Filaria nocturna occur in 
mosquitoes, a fact suggested almost simultaneously by Bancroft 
and Manson in 1877, and first demonstrated by the latter very soon 
thereafter. The experiments were first carried out with Culex 
quinqnefasciatus (= fatigans ) as a host, but it is now known that a 
number of species of mosquitoes, both anopheline and culicine, may 
serve equally well. 

When the blood of an infested individual is sucked up and reaches 
the stomach of such a mosquito, the larvas, by very active movements, 
escape from their sheaths and within a very few hours actively mi¬ 
grate to the body cavity of their new host and settle down primarily 
in the thoracic muscles. There in the course of sixteen to twenty 
days they undergo a metamorphosis of which the more conspicuous 
features are the formation of a mouth, an alimentary canal and a 
trilobed tail. At the same time there is an enormous increase in 
size, the larvae which measured .3 mm. in the blood becoming 1.5 mm. 
in length. This developmental period may be somewhat shortened 
in some cases and on the other hand may be considerably extended. 
The controlling factor seems to be the one of temperature. 

The transformed larvae then reenter the body cavity and finally 
the majority of them reach the interior of the labium (fig. 120). A 
few enter the legs and antennae, and the abdomen, but these are 
wanderers which, it is possible, may likewise ultimately reach the 
labium, where they await the opportunity to enter their human host. 



Filariasis and Mosquitoes 


181 


It was formerly supposed that when the infested mosquito punc¬ 
tured the skin of man, the mature larvae were injected into the cir¬ 
culation. The manner in which this occurred was not obvious, for 
when the insect feeds it inserts only the stylets, the labium itself 
remaining on the surface of the skin. Fiillebom has cleared up the 
question by showing that at this time the filariae escape and, like 
the hookworm, actively bore into the skin of their new host. 

Once entered, they migrate to the lymphatics and there quickly 
become sexually mature. The full grown females measure 85-90 mm. 
in length by .24-28 mm. in diameter, while the males are less than 



120. Filaria in the muscles and labium of Culex. After Blanchard. 


half this size, being about 40 mm. by .1 mm. Fecundation occurs 
and the females will be found filled with eggs in various stages of 
development, for they are normally viviparous. 

Filaria philippinensis is reported by Ashbum and Craig (1907) as 
a common blood filaria in the Philippine Islands. As they describe 
it, it differs from Filaria bancrofti primarily in that it does not exhibit 
periodicity. Its development has been found to occur in Cidex 
quinquejasciatus , where it undergoes metamorphosis in about fourteen 
or fifteen days. There is doubt as to the species being distinct from 
bancrofti. 

Several other species occur in man and are thought to be trans¬ 
ferred by various insects, among which have been mentioned Taba- 
nidse and tsetse-flies, but there is no experimental proof in support 
of such conjectures. 





182 Arthropods as Essential Hosts of Pathogenic Organisms 

Filaria immitis is a dangerous parasite of the dog, the adult worm 
living in the heart and veins of this animal. It is one of the species 
which has been clearly shown to undergo its development in the 
mosquito, particularly in Anopheles maculipennis and Aedes calopus 
(= Stegomyia). The larval form occurs in the peripheral blood, 
especially at night. When taken up by mosquitoes they differ from 
Filaria hancrofti in that they undergo their development in the 
Malpighian tubules rather than in the thoracic muscles. In 
about twelve days they have completed their growth in the tubules, 
pierce the distal end, and pass to the labium. This species occurs 
primarily in China and Japan, but is also found in Europe and in the 
United States. It is an especially favorable species for studying 
the transformations in the mosquito. 

Filar ice are also commonly found in birds, and in this country 
this is the most available source of laboratory material. We have 
found them locally (Ithaca, N. Y.) in the blood of 
over sixty per cent of all the crows examined, at 
any season of the year, and have also found them 
in English sparrows. 

In the crows, they often occur in enormous 
numbers, as many as two thousand having been 
found in a single drop of the blood of the most 
heavily infested specimen examined. For study, a 
small drop of blood should be mounted on a clean 
slide and the coverglass rung with vaseline or oil 
to prevent evaporation. In this way they can 
be kept for hours. 

Permanent preparations may be made by 
spreading out the blood in a film on a perfectly 
clean slide and staining. This is easiest done by touching the fresh 
drop of blood with the end of a second slide which is then held at 
an angle of about 45 0 to the first slide and drawn over it without 
pressure. Allow the smear to dry in the air and stain in the usual 
way with hematoxylin. 

Other Nematode Parasites of Man and Animals Developing 

in Arthropods 

Dracunculus medinensis (fig. 121), the so-called guinea-worm, is 
a nematode parasite of man which is widely distributed in tropical 
Africa, Asia, certain parts of Brazil and is occasionally imported 
into North America. 



121. Dracunculus 
medinensis; female; 
mouth; embryo. 
After Bastian and 
Leuckart. 






Other Nematodes Developing in Arthropods 


183 



122. Cyclops, the 
intermediate host of 
Dracunculus. 


The female worm is excessively long and slender, measuring nearly 
three feet in length and not more than one-fifteenth of an inch in 
diameter. It is found in the subcutaneous connective tissue and when 
mature usually migrates to some part of the leg. 

Here it pierces the skin and there is formed a small 
superficial ulcer through which the larvae reach the 
exterior after bursting the body of the mother. 

Fedtschenko (1879) found that when these larvae 
reach the water they penetrate the carapace of the 
little crustacean, Cyclops (fig. 122). Here they molt 
several times and undergo a metamorphosis. Fedts¬ 
chenko, in Turkestan, found that these stages required 
about five weeks, while Manson who confirmed these 
general results, found that eight or nine weeks were 
required in the cooler climate of Engand. 

Infection of the vertebrate host probably occurs through swallow¬ 
ing infested cyclops in drinking water. Fedtschenko was unable to 
demonstrate this experimentally and objection has been raised against 
the theory, but Leiper (1907), and Strassen (1907) succeeded in infest¬ 
ing monkeys by feeding them on cyclops containing the larvae. 

Habronema muscce is a worm which has long been known in its 
larval stage, as a parasite of the house-fly. Carter found them in 
33 per cent of the house-flies examined in Bombay during July, i860, 
and since that time they have been shown to be very widely distrib¬ 
uted. Italian workers reported them in 12 per cent to 30 per cent 
of the flies examined. Hewitt reported finding it rarely in England. 
In this country it was first reported by Leidy who found it in about 
20 per cent of the flies examined at Philadelphia, Pa. Since then it 
has been reported by several American workers. We have found it 
at Ithaca, N. Y., but have not made sufficient examinations to justify 
stating percentage. Ransom (1913) reports it in thirty-nine out of 
one hundred and thirty-seven flies, or 28 per cent. 

Until very recently the life-history of this parasite was unknown 
but the thorough work of Ransom (1911, 1913) has shown clearly 
that the adult stage occurs in the stomach of horses. The embryos, 
produced by the parent worms in the stomach of the horse, pass 
out with the feces and enter the bodies of fly larvae which are develop¬ 
ing in the manure. In these they reach their final stage of larval 
development at about the time the adult flies emerge from the pupal 
stage. In the adult fly they are commonly found in the head. 



184 Arthropods as Essential Hosts oj Pathogenic Organisms 



123. An Echinorhynchid, showing the spinose retractile proboscis. 




124. June beetle (Lachnosterna). Larva 

frequently in the proboscis, but they occur also in the thorax and 
abdomen. Infested flies are accidentally swallowed by horses and 
the parasite completes its development to maturity in the stomach of 
its definitive host. 







Other Nematodes developing in Arthropods 185 

Gigantorhynchus hirudinaceus (= Echinorhynchus gigas) is a com¬ 
mon parasite of the pig and has been reported as occurring in man. 
The adult female is 20-35 cm. long and 4-9 mm. in diameter. 
It lacks an alimentary canal and is provided with a strongly spined 
protractile rostrum, by means of which it attaches to the intestinal 
mucosa of its host. 

The eggs are scattered with the feces of the host and are taken 
up by certain beetle larvae. In Europe the usual intermediate hosts 
are the larvae of the cockchafer, Melolontha vulgaris, or of the flower 
beetle, Cetonia aurata. Stiles has shown that in the United States 
the intermediate host is the larva of the June bug, Lachnosterna 
(fig. 124). It is probable that several of the native species serve in 
this capacity. 

A number of other nematode parasites of birds and mammals 
have been reported as developing in arthropods but here, as in the 
case of the cestodes, experimental proof is scant. The cases above 
cited are the better established and will serve as illustrations. 


CHAPTER VIII 


ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC 
PROTOZOA 

Mosquitoes and Malaria 

Under the name of malaria is included a group of morbid symp¬ 
toms formerly supposed to be due to a miasm or bad air, but now 
known to be caused by protozoan parasites of the genus Plasmodium , 
which attack the red blood corpuscles. It occurs in paroxysms, 
each marked by a chill, followed by high fever and sweating. The 
fever is either intermittent or remittent. 

There are three principal types of the disease, due to different 
species of the parasite. They are: 

1. The benign-tertian, caused by Plasmodium vivax, which under¬ 
goes its schizogony or asexual cycle in the blood in forty-eight hours 
or even less. This type of the disease,—characterized by fever 
every two days, is the most wide-spread and common. 

2. The quartan fever is due to the presence of Plasmodium 
malaria, which has an asexual cycle of seventy-two hours, and there¬ 
fore the fever recurs every three days. This type is more prevalent 
in temperate and sub-tropical regions, but appears to be rare every¬ 
where. 

3. The sub-tertian “aestivo-autumnal,” or “pernicious” fever 
is caused by Plasmodium falciparum. Schizogony usually occurs 
in the internal organs, particularly in the spleen, instead of in the 
peripheral circulation, as is the case of the tertian and quartan forms. 
The fever produced is of an irregular type and the period of schizogony 
has not been definitely determined. It is claimed by some that the 
variations are due to different species of malignant parasites. 

It is one of the most wide-spread of human diseases, occurring 
in almost all parts of the world, except in the polar regions and in 
waterless deserts. It is most prevalent in marshy regions. 

So commonplace is malaria that it causes little of the dread 
inspired by most of the epidemic diseases, and yet, as Ross says, 
it is perhaps the most important of human diseases. Figures regard¬ 
ing its ravages arc astounding. Celli estimated that in Italy it 
caused an average annual mortality of fifteen thousand, representing 
about two million cases. In India alone, according to Ross (iqio) 


Mosquitoes and Malaria 


187 


“it has been officially estimated to cause a mean annual death-rate 
of five per thousand; that is, to kill every year, on the average, one 
million one hundred and thirty thousand.” In the United States 
it is widespread and though being restricted as the country develops, 
it still causes enormous losses. During the year 1911, “in Alabama 
alone there were seventy thousand cases and seven hundred and 
seventy deaths.” The weakening effects of the disease, the invasion 
of other diseases due to the attacks of malaria, are among the very 
serious results, but they cannot be estimated. 

Not only is there direct effect on man, but the disease has been one 
of the greatest factors in retarding the development of certain regions. 
Everywhere pioneers have had to face it, and the most fertile regions 
have, in many instances been those most fully dominated by it. 
Herrick (1903) has presented an interesting study of its effects on 
the development of the southern United States and has shown that 
some parts, which are among the most fertile in the world, are 
rendered practically uninhabitable by the ravages of malaria. How¬ 
ard (1909) estimates that the annual money loss from the disease 
in the United States is not less than $100,000,000. 

It was formerly supposed that the disease was due to a miasm, 
to a noxious effluvia, or infectious matter rising in the air from 
swamps. In other words its cause was, as the name indicated 
“mal aria,” and the deep seated fear of night air is based largely on 
the belief that this miasm was given off at night. Its production 
was thought to be favored by stirring of the soil, dredging operations 
and the like. 

The idea of some intimate connection between malaria and 
mosquitoes is not a new one. According to Manson, Lancisi noted 
that in some parts of Italy the peasants for centuries have believed 
that malaria is produced by the bite of mosquitoes. Celli states 
that one not rarely hears from such peasants the statement that 
“In such a place, there is much fever, because it is full of mosquitoes.” 
Koch points out that in German East Africa the natives call malaria 
and the mosquito by the same name, Mbit. The opinion was not 
lacking support from medical men. Celli quotes passages from the 
writings of the Italian physician, Lancisi, which indicate that he 
favored the view in 1717. 

Dr. Josiah Nott is almost universally credited with having sup¬ 
ported the theory, in 1848, but as we have already pointed out 
his work has been misinterpreted. The statements of Beauperthuy, 
(1853) were more explicit. 


iSS 


Arthropods as Hosts of Pathogenic Protozoa 


The clearest early presentation of the circumstantial evidence in 
favor of the theory of mosquito transmission was that of A. F. A. 
King, an American physician, in 1883. He presented a series of 
epidemiological data and showed “how they may be explicable by 
the supposition that the mosquito is the real source of the disease, 
rather than the inhalation or cutaneous absorption of a marsh vapor.” 
We may well give the space to summarizing his argument here for 
it has been so remarkably substantiated by subsequent work: 

1. Malaria, like mosquitoes, affects by preference low and moist 
localities, such as swamps, fens, jungles, marshes, etc. 

2. Malaria is hardly ever developed at a lower temperature 
than 6o° Fahr., and such a temperature is necessary for the develop¬ 
ment of the mosquito. 

3. Mosquitoes, like malaria, may both accumulate in and be 
obstructed by forests lying in the course of winds blowing from 
malarious localities. 

4. By atmospheric currents malaria and mosquitoes are alike 
capable of being transported for considerable distances. 

5. Malaria may be developed in previously healthy places by 
turning up the soil, as in making excavations for the foundation of 
houses, tracks for railroads, and beds for canals, because these opera¬ 
tions afford breeding places for mosquitoes. 

6. In proportion as countries, previously malarious, are cleared 
up and thickly settled, periodical fevers disappear, because swamps 
and pools are drained so that the mosquito cannot readily find a place 
suitable to deposit her eggs. 

7. Malaria is most dangerous when the sun is down and the 
danger of exposure after sunset is greatly increased by the person 
exposed sleeping in the night air. Both facts are readily explicable 
by the mosquito malaria theory. 

8. In malarial districts the use of fire, both indoors and to those 
who sleep out, affords a comparative security against malaria, because 
of the destruction of mosquitoes. 

9. It is claimed that the air of cities in some way renders the 
poison innocuous, for, though a malarial disease may be raging out¬ 
side, it does not penetrate far into the interior. We may easily 
conceive that mosquitoes, while invading cities during their nocturnal 
pilgrimages will be so far arrested by walls and houses, as well as 
attracted by lights in the suburbs, that many of them will in this 
way be prevented from penetrating “far into the interior.” 



Mosquitoes and Malaria 189 

10. Malarial diseases and likewise mosquitoes are most prevalent 
toward the latter part of summer and in the autumn. 

11. Various writers have maintained that malaria is arrested by- 
canvas curtains, gauze veils and mosquito nets and have recom¬ 
mended the use of mosquito curtains, “through which malaria can 
seldom or never pass.” It can hardly be conceived that these 
intercept marsh-air but they certainly do protect from mos¬ 
quitoes. 

12. Malaria spares no age, but it affects infants much less 
frequently than adults, because young infants are usually carefully 
housed and protected from mosquito inoculation. 

Correlated with the miasmatic theory was the belief that some 
animal or vegetable organism which lived in marshes, produced 
malaria, and frequent searches were made for it. Salisbury (1862) 
thought this causative organism to be an alga, of the genus Palmella; 
others attributed it to certain fungi or bacteria. 

In 1880, the French physician, Laveran, working in Algeria, 
discovered an amoeboid organism in the blood of malarial patients 
and definitely established the parasitic nature of this disease. Pig¬ 
mented granules had been noted by Meckel as long ago as 1847, in 
the spleen and blood of a patient who had died of malaria, and his 
observations had been repeatedly verified, but the granules had been 
regarded as degeneration products, and the fact that they occurred 
in the body of a foreign organism had been overlooked. 

Soon after the discovery of the parasites in the blood, Gerhardt 
(1884) succeeded in transferring the disease to healthy individuals 
by inoculation of malarious blood, and thus proved that it is a true 
infection. This was verified by numerous experimenters and it 
was found that inoculation with a very minute quantity of the dis¬ 
eased blood would not only produce malaria but the particular type 
of disease. 

Laveran traced out the life cycle of the malarial parasite as it 
occurs in man. The details as we now know them and as they are 
illustrated by the accompanying figure 125, are as follows: 

The infecting organism or sporozoite, is introduced into the cir¬ 
culation, penetrates a red blood corpuscle, and forms the amoeboid 
schizont. This lives at the expense of the corpuscle and as it develops 
there are deposited in its body scattered black or reddish black 
particles. These are generally called melanin granules, but are 
much better referred to as ha?mozoin, as they arc not related to 


190 Arthropods as Hosts of Pathogenic Protozoa 

melanin. The haemozoin is the most conspicuous part of the para¬ 
site, a feature of advantage in diagnosing from unstained prepara¬ 
tions. 

As the schizont matures, its nucleus breaks up into a number of 
daughter nuclei, each with a rounded mass of protoplasm about it, 
and finally the corpuscles are broken down and these rounded bodies 



125. Life cycle of the malaria parasite. Adapted from Leuckart’s chart, 
by Miss Anna Stryke. 


are liberated in the plasma as merozoites. These merozoites infect 
new corpuscles and thus the asexual cycle is continued. The malarial 
paroxysm is coincident with sporulation. 

As early as Laveran’s time it was known that under conditions 
not yet determined there are to be found in the blood of malarious 
patients another phase of the parasite, differing in form according 
to the type of the disease. In the pernicious type these appear as 
large, crescent-shaped organisms which have commonly been called 
“crescents.” We now know that these are sexual forms. 







Mosquitoes and Malaria 


191 

When the parasite became known there immediately arose specu¬ 
lations as to the way in which it was transferred from man to man. 
It was thought by some that in nature it occurred as a free-living 
amoeba, and that it gained access to man through being taken up 
with impure water. However, numerous attempts to infect healthy 
persons by having them drink or inhale marsh water, or by injecting 
it into their circulation resulted in failure, and influenced by Leuckart’s 
and Melnikoff’s work on Dipylidium, that of Fedtschenko on Dracun- 
culus, and more especially by that of Manson on Filaria, search was 
made for some insect which might transfer the parasite. 

Laveran had early suggested that the role of carrier might be 
played by the mosquito, but Manson first clearly formulated the 
hyopthesis, and it was largely due to his suggestions that Ross in 
India, undertook to solve the problem. With no knowledge of the 
form or of the appearance in this stage, or of the species of mosquito 
concerned, Ross spent almost two and a half years of the most arduous 
w r ork in the search and finally in August, 1897, seventeen years 
after the discovery of the parasite in man, he obtained his first 
definite clue. In dissecting a “dappled-winged mosquito,” “every 
cell was searched and to my intense disappointment nothing what¬ 
ever was found, until I came to the insect’s stomach. Here, however, 
just as I was about to abandon the examination, I saw a very delicate 
circular cell, apparently lying amongst the ordinary cells of the organ 
and scarcely distinguishable from them. On looking further, 
another and another similar object presented itself. I now focused 
the lens carefully on one of these, and found that it contained a few 
minute granules of some black substance, exactly like the pigment of 
the parasite of malaria. I counted altogether twelve of these cells 
in the insect.” 

Further search showed that “the contents of the mature pigment 
cells did not consist of clear fluid but of a multitude of delicate, 
thread-like bodies which on the rupture of the parent cell, were poured 
into the body cavity of the insect. They were evidently spores.” 

With these facts established, confirmation and extension of 
Ross’s results quickly followed, from many different sources. We 
cannot trace this work in detail but will only point out that much 
of the credit is due to the Italian workers, Grassi, Bignami, and 
Bastianelli, and to Koch and Daniels. 

It had already been found that when fresh blood was mounted and 
properly protected against evaporation, a peculiar change occurred 


192 Arthropods as Hosts of Pathogenic Protozoa 

in these crescents after about half an hour’s time. From certain 
of them there were pushed out long whip-like processes which moved 
with a very active, lashing movement. The parasite at this stage 
is known as the “flagellated body.” Others, differing somewhat in 
details of structure, become rounded but do not give off “flagella.” 

The American worker, MacCallum (1897), in studying bird 
malaria as found in crows, first recognized the true nature of these 
bodies. He regarded them as sexual forms and believed that the 
so-called flagella played the part of spermatozoa. Thus, the “flagel¬ 
lated body” is in reality a microgametoblast, producing micro gametes, 
or the male sexual element, while the others constitute the macro¬ 
gametes, or female elements. 

It was found that when blood containing these sexual forms was 
sucked up by an Anopheline mosquito and taken into its stomach, a 
microgamete penetrated and fertilized a macrogamete in a way 
analogous to what takes place in the fertilization of the egg in higher 
forms. The resultant, mobile organism is known as the migratory 
ookinete. In this stage the parasite bores through the epithelial 
lining of the “stomach” (mid-intestine) of the mosquito and becomes 
encysted under the muscle layers. Here the oocyst, as it is now 
known, matures and breaks up into the body cavity and finally 
its products come to lie in the salivary glands of the mosquito. Ten 
to twelve days are required for these changes, after which the mos¬ 
quito is infective, capable of introducing the parasite with its saliva, 
when feeding upon a healthy person. 

Thus the malarial parasite is known to have a double cycle, an 
alternation of generations, of which the asexual stage is undergone in 
man, the sexual in certain species of mosquitoes. The mosquito is 
therefore the definitive host rather than the intermediate, as usually 
stated. 

The complicated cycle may be made clearer by the diagram of 
Miss Stryke (1912) which, by means of a double-headed mosquito 
(fig. 126) endeavors to show how infection takes place through the 
biting of the human victim, (at A), in whom asexual multiplication 
then takes place, and how the sexual stages, taken up at B in the 
diagram, arc passed in the body of the mosquito. 

The experimental proof that mosquitoes of the Anopheline group 
are necessary agents in the transmission of malaria was afforded in 
1900 when two English physicians, Drs. Sambon and Low lived for 
the three most malarial months in the midst of the Roman Campagna, 


Mosquitoes and Malaria 


193 


a region famous for centuries as a hot-bed of malaria. The two 
experimenters moved about freely throughout the day, exposed 



126. Life cycle of the malarial parasite. After Miss Anna Stryke. 


themselves to rains and all kinds of weather, drank marsh water, 
slept exposed to the marsh air, and, in short, did everything which 
was supposed to cause malaria, except that they protected them¬ 
selves thoroughly from mosquito bites, retiring at sunset to a mosquito- 







194 Arthropods as Hosts of Pathogenic Protozoa 

'proof hut. Though they took no quinine'and all of their neighbors 
suffered from malaria, they were absolutely free from the disease. 

To complete the proof, mosquitoes which had fed in Rome on 
malarious patients were sent to England and allowed to bite two 
volunteers, one of them Dr. Manson’s own son, who had not been 
otherwise exposed to the disease. Both of these gentlemen con¬ 
tracted typical cases of malaria and the parasites were to be found in 
abundance in their blood. 

Since that time there have been many practical demonstrations 
of the fact that malaria is transmitted exclusively by the bite of 

mosquitoes and that the destruc¬ 
tion of the mosquitoes means the 
elimination of the disease. 

We have said that the malarial 
parasite is able to undergo its 
development only in certain 
species of mosquitoes belonging 
to the Anopheline group. It is 
by no means certain that all of 
this group even, are capable of 
acting as the definitive host of 
the parasites, and much careful 
experiment work is still needed 
along this line. In the United 
States, several species have been 
found to be implicated, Anopheles 
quadrimaculatus and Anopheles 
crucians being the most common. The characteristics of these species 
and the distinctions between them and other mosquitoes will be 
discussed in Chapter XII. 

In antimalarial work it is desirable to distinguish the anopheline 
mosquitoes from the culicine species in all stages. The following 
tabulation presents the more striking distinctions between the groups 
as represented in the United States. 

Anopheles Culex, Aedes, etc. 

Eggs: Laid singly in small Deposited in clumps in the 
numbers upon the surface of the form of a raft (Culex group) or 
water. Eggs lie upon their sides deposited singly in the water or 
and float by means of lateral on the ground in places which 
expansions (fig. 127). may later be submerged. 



127. Eggs of Anopheles. After Howard. 


Mosquitoes and Malaria 


195 


Larva: When at rest floats in 
a horizontal position beneath the 
surface film. No respiratory 
tube but instead a flattened 
area on the eighth abdominal 
segment into which the two 
spiracles open (fig. 128). 

Adults: Palpi in both sexes 
nearly or quite as long as the 
proboscis. Proboscis projecting 
forward nearly on line with the 
axis of the body. When at rest 
on a vertical wall the body is 
usually held at an angle with the 
vertical (fig. 128). Wings fre¬ 
quently spotted (fig. 130). 


When at rest (with few excep¬ 
tions) floats suspended in an 
oblique or vertical position, or 
more rarely nearly horizontal, 
with the respiratory tube in 
contact with the surface film 
(fig. .128). 

Palpi short in the female, in 
the male usually elongate. Pro¬ 
boscis projects forward at an 
angle with the axis of the body. 
When at rest on a vertical wall 
the body is usually held parallel 
or the tip of the abdomen in¬ 
clined towards the wall (fig. 128). 
Wings usually not spotted. 



(a) Normal position of the lar¬ 
vae of Culex and Anopheles in 
the water. Culex. left; Ano¬ 
pheles, middle; Culex pupa, 
right hand figure. 


These malarial-bearing species are essentially domesticated 
mosquitoes. They develop in any accumulation of water which 

stands for a week or more. 
Ponds, puddles, rain barrels, 
horse troughs, cess-pools, cans, 
even the foot-prints of ani¬ 
mals in marshy ground may 
afford them breeding places. 
It is clear from what has been said regarding the life cycle of the 
malarial parasite that the mosquito is harmless if not itself diseased. 
Hence malarial-bearing species may abound in the 
neighborhood where there is no malaria, the disease 
being absent simply because the mosquitoes are unin¬ 
fected. Such a locality is potentially malarious and 
needs only the introduction of a malarial patient who is 
exposed to the mosquitoes. It is found that such patients 
may harbor the parasites in their blood long after they 
are apparently well and thus may serve as a menace, 
just as do the so-called typhoid carriers. In some 
malarious regions as high as 80-90 per cent of the natives 
are such malaria-carriers and must be reckoned with in 
antimalaria measures. 128 (6) Norma 

Based upon our present day knowledge of the life cycle c°u S i'e x° n a ni 

of the malarial parasite the fight against the disease fh n e °waiL S °" 






196 


Arthropods as Hosts of Pathogenic Protozoa 



becomes primarily a problem in economic entomology, — it is a ques¬ 
tion of insect control, in its broadest interpretation. 

The lines of defence and offence 
against the disease as outlined by 
Boyce (1909) are - 

1. Measures to avoid the reser¬ 
voir (man): 

vSegregation. 

Screening of patients. 

2. Measures to avoid Anopheles: 
Choice of suitable locality, 

when possible. 

Screening of houses and 
porches. 

Sleeping under mosquito nets. 

3. Measures to exterminate the 
Anopheles: 

Use of natural enemies. 

Use of culirides, oiling ponds, 
etc. 

Drainage and scavenging to 
destroy breeding places. 
Enforcement of penalties for 
harboring larvae or keeping 

129. Larva of Anopheles. After Howard. Stagnant Water. 

Educational methods. 

4. Systematic treatment with quinine to exterminate theparasites. 


Mosquitoes and Yellow Fever 

Yellow fever was until recently one of the most dreaded of epi¬ 
demic diseases. It is an acute, specific and infectious disease, non- 
contagious in character but occurring in epidemics, or endemics, 
within a peculiarly limited geographical area. It is highly fatal, 
but those who recover are generally immune from subsequent at¬ 
tacks. 

It is generally regarded as an American disease, having been 
found by Cortez, in Mexico, and being confined principally to the 
American continents and islands. It also occurs in Africa and at¬ 
tempts have been made to show that it was originally an African 
disease but there is not sufficient evidence to establish this view. 



Mosquitoes and Yellow Fever 


197 


There have been many noted outbreaks in the United States. 
Boston suffered from it in 1691 and again in 1693; New York in 
1668 and as late as 1856; Baltimore in 1819. In 1793 occurred the 
great epidemic in Philadelphia, with a death rate of one in ten of the 
population. In the past century it was present almost every year in 
some locality of our Southern States, New Orleans being the greatest 
sufferer. In the latter city there were 7848 deaths from the disease 
in 1853, 4854 in 1858, and 4046 in 1878. The last notable outbreak 



130. Anopheles quadrimaculatus, male and female, (x3>p. After Howard. 

was in 1905. Reed and Carroll (1901) estimated that during the 
period from 1793 to 1900 there had not been less than 500,000 cases 
in the United States. 

As in the case of the plague, the most stringent methods of con¬ 
trol proved ineffective and helplessness, almost hopelessness marked 
the great epidemics. A vivid picture of conditions is that given by 
Mathew Cary, 1793 (quoted by Kelly, 1906) in “A Short Account of 
the Malignant Fever Lately Prevalent in Philadelphia.” 

The consternation of the people of Philadelphia at this period 
was carried beyond all bounds. Dismay and affright were visible 



198 Arthropods as Hosts of Pathogenic Protozoa 

in the countenance of almost every person. Of those who remained, 
many shut themselves in their houses and were afraid to walk the 
streets. * * * The corpses of the most respectable citizens, 

even those who did not die of the epidemic, were carried to the grave 
on the shafts of a chair (chaise), the horse driven by a negro, un¬ 
attended by friends or relative, and without any sort of ceremony. 



People hastily shifted their course at the sight of a hearse coming 
toward them. Many never walked on the footpath, but went into 
the middle of the streets to avoid being infected by passing by houses 
wherein people had died. Acquaintances and friends avoided each 
other in the streets and only signified their regard by a cold nod. 
The old custom of shaking hands fell into such disuse that many 
shrunk back with affright at even the offer of the hand. A person 





Mosquitoes and Yellow Fever 


199 


with a crape, or any appearance of mourning was shunned 1 ke a 
viper. And many valued themselves highly on the skill and address 
with which they got to the windward of every person they met. 
Indeed, it is not probable that London, at the last stage of the plague, 
exhibited stronger marks of terror than were to be seen in Phila- 



132. Anopheles crucians. Female (X 4 ). After Howard. 


delphia from the 24th or 25th of August until pretty late in Septem¬ 
ber.” 

Such was the condition in Philadelphia in 1793 and, as far as 
methods of control of the disease were concerned, there was practi¬ 
cally no advance during the last century. The dominant theory 
was that yellow fever was spread by foniites, that is, exposed bedding, 
clothing, baggage, and the like. As late as 1898 a bulletin of the 
United States Marine Hospital Service stated: 





200 


Arthropods as Hosts of Pathogenic Protozoa 


“While yellow fever is a communicable disease, it is not con¬ 
tagious in the ordinary acceptance of the term, but is spread by the 
infection of places and articles of bedding, clothing, and furniture.” 

Based upon this theory, houses, baggage, freight, even mail, 
were disinfected, and the most rigid quarantine regulations were 
enforced. The hardships to which people of the stricken regions 
were subjected and the financial losses are incalculable. And withal, 
the only efficient check upon the disease seemed to be the heavy frosts. 



/ \ 


/ \ 

/ \ 

\ 

133. Culex sollicitans. Female (X 4 ). After Howard. 

It was found that for some reason, the epidemic abated with cold 
weather,—a measure beyond human control. 

It is not strange that among the multitude of theories advanced to 
explain the cause and method of dissemination of the disease there 
should be suggestions that yellow fever was transmitted by the 
mosquito. We have seen that Beauperthuy (1855) clearly urged 
this theory. 

More detailed, and of the greatest influence in the final solution 
of the problem were the arguments of Dr. Carlos Finlay, of Havana. 
In 1881, in a paper presented before the “Rea Academia de Cicncias 
M^dicas, Fisicis y Naturales dc la Habana,” he said: 


Mosquitoes and Yellow Fever 


201 


‘ ‘ I feel convinced that any theory which attributes the origin and 
the propagation of yellow fever to atmospheric influences, to mias¬ 
matic or meteorological conditions, to filth, or to the neglect of general 
hygienic precautions, must be considered as utterly indefensible.” 

He postulated the existence of a material transportable substance 
causing yellow fever,—“something tangible which requires to be 
conveyed from the sick to the healthy before the disease can be 
propagated” and after discussing the peculiarities of the spread of 
the disease and the influence of meteorological conditions, he decides 
that the carriers of the disease must be sought among insects. He 
continues: 

“On the other hand, the fact of yellow fever being characterized 
both clinically and (according to recent findings) histologically, by 
lesions of the blood vessels and by alterations of the physical and 
chemical conditions of the blood, suggested that the insect which 
should convey the infectious particles from the patient to the healthy 
should be looked for among those which drive their sting into blood 
vessels in order to suck human blood. Finally, by reason of other 
considerations which need not be stated here, I came to think that 
the mosquito might be the transmitter of yellow fever.” 

“Assimilating the disease to small-pox and to vaccination, it 
occurred to me that in order to inoculate yellow fever it would be 
necessary to pick out the inoeulable material from within the blood 
vessels of a yellow fever patient and to carry it likewise into the 
interior of a blood vessel of a person who was to be inoculated. All 
of which conditions the mosquito satisfies most admirably through 
its bite.” 

In the course of his study of the problem, Finlay made detailed 
studies of the life history and habits of the common mosquitoes at 
Havana, and arrived at the conclusion that the carrier of the yellow 
fever was the Culex mosquito or A 'edes calopus, as it is now known. 
With this species he undertook direct experimental tests, and be¬ 
lieved that he succeeded in transmitting the disease by the bite of 
infected mosquitoes in three cases. Unfortunately, possibility 
of other exposure was not absolutely excluded, and the experiments 
attracted little attention. 

Throughout the next twenty years Finlay continued his work on 
yellow fever, modifying his original theory somewhat as time went on. 
Among his later suggestions was that in the light of Smith’s work 
on Texas fever, his theory must be “somewhat modified so as to 


202 


Arthropods as Hosts of Pathogenic Protozoa 


include the important circumstance that the faculty of transmitting 
the yellow fever germ need not be limited to the parent insect, 
directly contaminated by stinging a yellow fever patient (or per¬ 
haps by contact with or feeding from his discharges), but may be 
likewise inherited by the next generation of mosquitoes issued from 
the contaminated parent.” He believed that the bite of a single 
mosquito produced a light attack of the disease and was thus effec¬ 
tive in immunizing the patient. Throughout the period, many 
apparently successful attempts to transmit the disease by mosqui¬ 
toes were made. In the light of present day knowledge we must 
regard these as defective not only because possibility of other infec¬ 
tion was not absolutely excluded but because no account was taken 
of the incubation period within the body of the mosquito. 

In 1900, while the American army was stationed in Cuba there 
occurred an epidemic of yellow fever and an army medical board was 
appointed for‘‘the purpose of pursuing scientific investigations with 
reference to the acute infectious diseases prevalent on the island.” 
This was headed by Walter Reed and associated with him were James 
Carroll, Jesse W. Lazear and Aristides Agramonte, the latter a Cuban 
immune. For a detailed summary of this work the lay reader can¬ 
not do better than read Dr. Kelly’s fascinating biography ‘‘Walter 
Reed and Yellow Fever.” 

Arriving at the army barracks near Havana the Commission first 
took up the study of Bacillus icteroides, the organism which Sanarelli, 
an Italian physician, had declared the causative agent in yellow fever. 
They were unable to isolate this bacillus either from the blood during 
life or from the blood and organs of cadavers and therefore turned 
their attention to Finlay’s theory of the propagation of yellow fever 
by means of the mosquito. In this work they had the unselfish 
and enthusiastic support of Dr. Finlay himself, who not only consulted 
with them and placed his publications at their disposal, but furnished 
eggs from which their experimental mosquitoes were obtained. 
Inoculations of eleven non-immunes through the bite of infected 
mosquitoes were made, and of these, two gave positive results. The 
first of the two was Dr. Carroll who allowed himself to be bitten 
by a mosquito which had been caused to feed upon four cases of 
yellow fever, two of them severe and two mild. The first patient 
had been bitten twelve days before. 

Three days after being bitten, Dr. Carroll came down with a 
typical case of yellow fever. So severe was the attack that for three 


Mosquitoes and Yellow Fever 


203 


days his life hung in the balance. During his convalescence an 
incident occurred which showed how the theory of mosquito trans¬ 
mission of the disease was generally regarded. We quote from Dr. 
Kelly: “One of his nurses who came from Tennessee had had con¬ 
siderable experience with yellow fever, having indeed, lost her hus¬ 
band and several children from it. One day early in his illness Dr. 
Carroll mentioned to her that he had contracted the disease through 
the bite of a mosquito, and noticed that she looked surprised. Some 
time later, when well enough to look over the daily records of his 
condition, he found this entry: ‘Says he got his illness through the 
bite of a mosquito,—delirious’.” 

The second case was that of an American who was bitten by four 
mosquitoes, two of which had bitten severe (fatal) cases of yellow 
fever twelve days previously, one of which had bitten a severe case 
(second day) sixteen days before and one which had bitten a severe 
case eight days before. Five days later, the subject developed a well 
pronounced but mild case of the disease. 

In the meantime, another member of the Commission, Dr. Lazear, 
was accidentally bitten by a mosquito while collecting blood from 
yellow fever patients. Five days later he contracted a typical case 
which resulted fatally. 

So clear was the evidence from these preliminary experiments 
that the commission felt warranted in announcing, October 27, 1900, 
that, “The mosquito serves as the intermediate host for the parasite 
of yellow fever, and it is highly probable that the disease is only 
propagated through the bite of this insect.” 

In order to extend the experimental evidence under conditions 
which could leave no possibility of infection from other sources, a 
special experimental sanitary station, named in honor of the deceased 
member of the Commission, was established in an open field near 
the town of Quemados, Cuba. Here there were constructed two small 
buildings known respectively as the “infected clothing building” 
and the “infected mosquito building.” 

The infected clothing building, 14 x 20 feet in size, was purposely 
so constructed as to exclude anything like efficient ventilation, but 
was thoroughly screened to prevent the entrance of mosquitoes. 
Into this building were brought sheets, pillow-slips, blankets, etc., 
contaminated by contact with cases of yellow fever and their dis¬ 
charges, — many of them purposely soiled with a liberal quantity of 
black vomit, urine, and fecal matter from patients sick with yellow 


204 Arthropods as Hosts of Pathogentc Protozoa 

fever. Nothing could better serve as the fomites which were sup¬ 
posed to convey the dread disease. 

Three non-immunes unpacked these articles, giving each a 
thorough handling and shaking in order to disseminate through the 
air of the room the specific agent of the disease. They were then 
used in making up the beds which the volunteers occupied each night 
for a period of twenty days. The experiment was repeated three 
times, volunteers even sleeping in the soiled garments of yellow fever 
victims but in not a single case was there the slightest symptom of 
disease. The theory of the spread of yellow fever by fomites was 
completely demolished. 

The infected mosquito building, equal in size to its companion, 
was the antithesis as far as other features were concerned. It was 
so constructed as to give the best possible ventilation, and bedding 
which was brought into it was thoroughly sterilized. Like the 
infected clothing building it was carefully screened, but in this case 
it was in order to keep mosquitoes in it as well as to prevent entrance 
of others. Through the middle of the room ran a mosquito-proof 
screen. 

On December 5, 1900, a non-immune volunteer who had been in 
the quarantine camp for fifteen days and had had no other possible 
exposure, allowed himself to be bitten by five mosquitoes which had 
fed on yellow fever patients fifteen or more days previously. The 
results were fully confirmatory of the earlier experiments of the 
Commission-—at the end of three days, nine and a half hours, the 
subject came down with a well marked case of yellow fever. 

In all, ten cases of experimental yellow fever, caused by the bite 
of infected mosquitoes were developed in Camp Lazear. Through¬ 
out the period of the disease, other non-immunes slept in the little 
building, separated from the patient only by the mosquito-proof 
screen, but in no circumstances did they suffer any ill effects. 

It was found that a yellow fever patient was capable of infecting 
mosquitoes only during the first three or four days after coming 
down with the disease. Moreover, after the mosquito has bitten 
such a patient, a period of at least twelve days must elapse before 
the insect is capable of transmitting the disease. 

Once the organism has undergone its twelve day development, 
the mosquito may remain infective for weeks. In experiments of 
the Commission, two of the mosquitoes transmitted the disease to a 
volunteer fiftv-seven davs after their contamination. No other 


Mosquitoes and Yellow Fever 


205 


volunteers presenting themselves, one of these mosquitoes died the 
sixty-ninth and one the seventy-first day after their original con¬ 
tamination, without it being determined whether they were still 
capable of transmitting the disease. 

So carefully carried out was this work and so conclusive were the 
results that Dr. Reed w^as justified in writing: 

“Six months ago, when we landed on this island, absolutely noth¬ 
ing was known concerning the propagation and spread of yellow 
fever—it was all an unfathomable mystery—but today the curtain 
has been drawn—its mode of propagation is established and we know 
that a case minus mosquitoes is no more dangerous than one of 
chills and fever.’’ 

The conclusions of the Commission were fully substantiated by 
numerous workers, notably Dr. Guiteras of the Havana Board of 
Health, who had taken a lively interest in the work and whose 
results were made known in 1901, and by the Brazilian and French 
Commission at Sao Paulo, Brazil, in 1903. 

Throughout the work of the Army Commission and down to the 
present time many fruitless efforts have been made to discover the 
specific organism of yellow fever. It was clearly established that 
the claims of Sanarelli for Bacillus icteroides were without founda¬ 
tion. It was found, too, that whatever the infective agent might 
be it was capable of passing through a Berkefeld filter and thus be¬ 
longs to the puzzling group of “filterable viruses.” It was further 
found that the virus was destroyed by heating up to 55° C for ten 
minutes. It is generally believed that the organism is a Protozoan. 

The question of the hereditary transmission of the yellow fever 
organism within the mosquito w r as left unsettled by the Army Com¬ 
mission, though, as w r e have seen, it was raised by Finlay. Marchoux 
and Simond, of the French Commission devoted much attention to 
this phase of the problem and basing their conclusions on one ap¬ 
parently positive case, they decided that the disease could be trans¬ 
mitted through the egg of an infected Aedes calopus to the second 
generation and thence to man. The conclusion, w r hich is of very 
great importance in the control of yellow fever, has not been verified 
by other workers. 

Once clearly established that yellow fever w T as transmitted solely 
by mosquitoes, the question of the characteristics, habits, and geo¬ 
graphical distribution of the insect parrier became of vital import¬ 


ance. 


206 Arthropods as Hosts of Pathogenic Protozoa 

A'cdes calopus, more commonly known as Stegomyia fasciata or 
Stegomyia calopus (fig. 134) is a moderate sized, rather strikingly 
marked mosquito. The general color is dark-brown or reddish- 
brown, but the thorax has a conspicuous broad, silvery-white curved 
line on each side, with two parallel median silvery lines. Between 

the latter there is a 
slender, broken line. 
The whole gives a lyre¬ 
shaped pattern to the 
thorax. The abdomen 
is dark with silvery- 
white basal bands and 
silvery white spots on 
each side of the ab¬ 
dominal segments. 
Legs black with rings 
of pure white at the 
base of the segments. 

Size of the female 
3.3 to 5 mm.; male 3 
to 4.5 mm. 

It is pre-eminently 
a domesticated species, 
being found almost 
exclusively about the 
habitation of man. 
“ Its long association 
with man is shown by 
many of its habits. It 
approaches stealthily 

134. The yellow fever mosquito (Aedes calopus), (.\7). from behind It re- 

After Howard. 

treats upon the slight¬ 
est alarm. The ankles and, when one is sitting at a table or desk, 
the underside of the hands and wrists are favorable points of attack. 
It attacks silently, whereas other mosquitoes have a piping or hum¬ 
ming note. The warning sound has doubtless been suppressed in 
the evolutionary process of its adaptation to man. It is extremely 
wary. It hides whenever it can, concealing itself in garments, 
working into the pockets, and under the lapels of coats, and crawl¬ 
ing up under the clothes to bite the legs. In houses, it will hide 






Mosquitoes and Yellow Fever 


207 


in dark comers, under picture moldings and behind the heads of 
old-fashioned bedsteads. It will enter closets and hide in the folds 
of garments.”—Howard. 

It was claimed by the French Commission, and subsequently 
often stated in discussions of the relation of the mosquito to yellow 
fever that the mature Aedes calopus will bite only at night. If this 
were true it would be of the greatest importance in measures to 
avoid the disease. Unfortunately, the claim was illy founded and 
numerous workers have clearly established that the exact converse 
is more nearly true, this mosquito being pre-eminently a day species, 
feeding most actively in early morning, 
about sunrise, and late in the afternoon. 

On cloudy days it attacks at any time 
during the day. Thus there is peril in 
the doctrine that infected regions may 
be visited with perfect safety during 
the daytime and that measures to 
avoid the mosquito attack need be 
taken only at night. 

Dr. Finlay maintained that the 
adult, even when stamed, would not 
bite when the temperature was below 
23 0 C, but subsequent studies have 
shown that this statement needs modi¬ 
fication. The French Commission, 
working at Rio de Janeiro, found that Aedes calopus would bite 
regularly at temperatures between 22 0 and 25 0 and that the optimum 
temperature was between 27 0 and 30° C, but their experiments led 
them to believe that it would bite in nature at a temperature as 
low as 17 0 C. 

The yellow fever mosquito breeds in cisterns, water barrels, 
pitchers and in the various water receptacles about the house. In 
our own Southern States it very commonly breeds in the above¬ 
ground cisterns which are in general use. Often the larvae (fig. 135 b) 
are found in flower vases, or even in the little cups of water which 
are placed under the legs of tables to prevent their being overrun by 
ants. They have been repeatedly found breeding in the holy water 
font in churches. In short, they breed in any collection of water in 
close proximity to the dwellings or gathering places of man. 



135a. Aedes calopus. Pupa. 
After Howard. 



2o8 


Arthropods as Hosts of Pathogenic Protozoa 



The life cycle under favorable conditions is completed in from 
twelve to fifteen days. These figures are of course very dependent 
upon the temperature. The Army Commission in Cuba found that 
the cycle might be completed in as brief a period as nine and a half 
days. Under less favorable conditions it may be greatly lengthened. 

The adults are long lived. We have 
seen that during the experimental work 
in Cuba specimens were kept in cap¬ 
tivity for sixty-nine and seventy-one 
days, respectively, and that they were 
proved to retain their infectivity for at 
least fifty-seven days. Dr. Guiteras 
subsequently kept an infected adult for 
one hundred and fifty-four days. 

Low temperatures have a very great 
effect not only on development, but on 
the activity and even life of the adults. 
Long before the method of transmission 
of yellow fever was discovered it was well 
known that the epidemics were brought 
to a close by heavy frosts, and it is now 
known that this is due to the killing of 
the mosquitoes which alone could spread 
the disease. 

Aedes calopus has a very wide distri¬ 
bution since, as Howard says, being a 
domestic mosquito, having a fairly long 
* life in the adult stage, and having the 
custom of hiding itself in the most ingen¬ 
ious ways, it is particularly subject to car¬ 
riage for long distances on board vessels, 
in railway trains, even packed in baggage. In general, its permanent 
distribution is from 40 degrees north latitude to 40 degrees south 
latitude (Brumpt), in a belt extending around the world. In the 
United States it breeds in most of our Southern States. 

Thus, as in the case of malaria, there are many places where the 
insect earner is abundant but where yellow fever does not occur. 
Such, for instance, are Hawaii, Australia and Asia. An outbreak may 
occur at any time that a patient suffering from the disease is allowed 
to enter and become a source of infection for the mosquitoes. In 


1356. Aedes calopus; larva. (x 7 ). 
After Howard. 









Mosquitoes and Yellow Fever 


209 


this connection various writers have called attention to the menace 
from the Panama Canal. When it is completed, it will allow of 
direct passage from regions where yellow fever is endemic and this 
will greatly increase the possibility of its introduction into these places 
where it is now unknown. The result, with a wholly non-immune 
population, would be appalling. 

On the other hand, there are places wholly outside of the normal 
range of Aedes calopus where the disease has raged. Such are New 
York, Boston, and even Philadelphia, which have suffered notable 
epidemics. These outbreaks have been due to the introduction of 
infected mosquitoes during the heat of summer, when they have not 
only conveyed the disease but have found conditions favorable 
for their multiplication. Or, uninfected mosquitoes have been thus 
accidentally brought in and developed in large numbers, needing 
then only the accidental introduction of cases of the disease to start 
an epidemic. 

Methods of control of various diseases have been revolutionized 
by the discovery that they were insect-borne, but in no other case 
has the change been as radical or the results as spectacular as in the 
case of yellow fever. The “shot-gun quarantine,” the sufferings and 
horrors, the hopelessness of fighting absolutely blindly have given 
way to an efficient, clear-cut method of control, based upon the knowl¬ 
edge that the disease is carried from man to man solely by the mosqui¬ 
to, Aedes calopus. The lines of defense and offense are essentially 
as follows: 

In the first place, when a case of yellow fever occurs, stringent 
precautions must be adopted to prevent the infection of mosquitoes 
and the escape of any already infected. This means that the patient 
must be removed to a mosquito-proof room, or ward beyond reach of 
the insects, and that the infected room must be thoroughly fumi¬ 
gated at once, to kill the mosquitoes hiding within it. All cracks 
and openings should be closed with strips of paper and fumigation 
with burning sulphur or pyrethrum carefully carried out. 

It should be remembered that if the first case noted is that of a 
resident rather than imported, it means that the mosquito carriers 
became infected more than two weeks before the case was diagnosed, 
for as we have seen, the germ must undergo a twelve-day period of 
development within its insect host. Therefore a careful search must 
be made for mild cases which, though unrecognized, may serve as 
foci for the spread of the disease. 


210 


Arthropods as Hosts of Pathogenic Protozoa 


In face of a threatened epidemic one of the most essential measures 
is to educate the citizens and to gain their complete cooperation in 
the fight along modem lines. This may be done through the schools, 
the pulpit, places of amusement, newspapers and even bulletin 
boards. 

Emphasis should be placed on the necessity of both non-immunes 
and immunes using mosquito curtains, and in all possible ways 
avoiding exposure to the mosquitoes. 

Then the backbone of the fight must be the anti-mosquito meas¬ 
ures. In general, these involve screening and fumigating against 
adults, and control of water supply, oiling, and drainage against the 
larvae. The region involved must be districted and a thorough survey 
undertaken to locate breeding places, which must, if possible, 
be eradicated. If they are necessary for water supplies, such as 
casks, or cisterns, they should be carefully screened to prevent 
access of egg-laying adults. 

The practical results of anti-mosquito measures in the fight 
against yellow fever are well illustrated by the classic examples of 
the work in Havana, immediately following the discoveries of the 
Army Commission and by the stamping out of the New Orleans 
epidemic in 1905. 

The opportunities for an immediate practical application of the 
theories of the Army Commission in Havana were ideal. The city 
had always been a hotbed of yellow fever and was the principal 
source from which the disease was introduced year after year into 
our Southern States. It was under martial law and with a military 
governor who was himself a physician and thoroughly in sympathy 
with the views of the Commission, the rigid enforcement of the 
necessary regulations was possible. The story of the first campaign 
has been often told, but nowhere more clearly than in Dr. Reed’s 
own account, published in the Journal of Hygiene for 1902. 

Closer home was the demonstration of the efficacy of these 
measures in controlling the yellow fever outbreak in New Orleans 
in 1905. During the spring and early summer of the year the disease 
had, unperceived, gained a firm foothold in that city and when, in 
early July the local Board of Health took cognizance of its existence, 
it was estimated that there had been in the neighborhood of one 
hundred cases. 

Conditions were not as favorable as they had been under martial 
law in Havana for carrying on a rigid fight along anti-mosquito lines. 


Mosquitoes and Yellow Fever 


211 


The densely populated city was unprepared, the public had to be 
educated, and an efficient organization built up. The local authori¬ 
ties actively began a general fight against the mosquito but in spite 
of their best efforts the disease continued to spread. It was recog¬ 
nized that more rigid organization was needed and on August 12 th 
the United States Public Health and Marine Hospital Sendee was 
put in absolute charge of the fight. Up to this time there had been 
one hundred and forty-two deaths from a total of nine hundred and 
thirteen cases and all of the conditions seemed to threaten an out¬ 
break to exceed the memorable one of 1878 when, as we have seen 
there were four thousand and forty-six deaths. 

With the hearty cooperation of the citizens, — physicians and 
laymen alike,—the fight was waged and long before frost or any near 
approach thereto the disease was stamped out, — a thing unheard of 
in previous epidemics. The total loss of life was four hundred and 
sixty — about 11 per cent as great as that from the comparable epi¬ 
demic of 1878. If the disease had been promptly recognized and 
combated with the energy which marked the fight later in the sum¬ 
mer, the outbreak would have made little headway and the great 
proportion of these lives would have been saved. 


CHAPTER IX 


ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA 

Insects and Trypanosomiases 

By trypanosomiasis is meant a condition of animal parasitism, 
common to man and the lower animals, in which trypanosomes, 
peculiar flagellate protozoa, infest the blood. Depending upon the 
species, they may be harmless, producing no appreciable ill-effect, 
or pathogenic, giving rise to conditions of disease. A number of 
these are known to be transferred by insects. 

In order that we may 
consider more fully the 
developmental stage of 
these parasites within 
their insect host, it is 
necessary that we des¬ 
cribe briefly the structure 
of the blood-inhabiting 
stage. 

The trypanosomes are 
elongated, usually point¬ 
ed, flagellated protozoa 
(fig. 136) in which the 
single flagellum, bent 
under the body, forms the 
outer limit of a delicate undulating membrane. It arises near 
one end of the organism from a minute centrosome-like body 
which is known as the blepheroplast, and at the opposite end extends 
for a greater or less distance as a free flagellum. Enclosing, or 
close beside the blepheroplast is the small kinetonucleus. The 
principal nucleus, round or oval in form, is situated near the center 
of the body. Asexual reproductions occurs in this stage, by longi¬ 
tudinal fission, the nucleus and the blepheroplast dividing independ¬ 
ently of one another. From the blepheroplast of one of the daughter 
cells a new flagellum is formed. 

Among the pathogenic species are to be found the causative 
organisms of some of the most serious diseases of domestic animals 
and even of man. It is probable that these pathogenic species secrete 



212 




Fleas and Lice as Carriers of Trypanosoma lewisi 213 

a specific poison. The majority of them are tropical in distri¬ 
bution. 

Though we are concerned especially with the species which infest 
man, we shall first consider two of the trypanosomes of lower animals, 
known long before any of those of man had been found. 

Fleas and Lice as Carriers of Trypanosoma lewisi .—Trypanosoma 
lewisi, the first mammalian trypanosome known, is to be found in the 
blood of wild rats. Like its host, it appears to be cosmopolitan in 
distribution, having been reported from several localities in the 
United States, Brazil, Argentine, England, Germany, France, Italy, 
Russia, Asia and Africa. 

This species is usually regarded as non-pathogenic, but in experi¬ 
mental work, especially with white rats, heavy infestations often 
result fatally, and naturally infested specimens sometimes show 
evidence of injury. Rats which have been infested exhibit at least 
temporary immunity against new infection. 

Trypanosoma lewisi is transmitted from rat to rat by fleas and 
by lice. Rabinowitsch and Kempner (1899) first found that healthy 
rats which were kept with infested rats, showed trypanosomes in 
their blood after about two weeks. They found the trypanosomes 
in the alimentary canal of fleas which had fed on the diseased rats. 
On teasing such fleas in physiological salt solution and inoculating 
them into fresh rats they were able to produce the infection. Finally, 
they showed that the fleas which had fed upon infested rats were 
able to carry the parasites to healthy rats. Corresponding experi¬ 
ments with lice were not successful. Prowazek G9°5) found in the 
rat louse ( Hceniatopinus spinulosus ) organisms which he regarded 
as developmental stages of the Trypanosoma lewisi. He believed 
that the sexual cycle was undergone in this insect. 

Nuttall (1908) readily transmitted the trypanosomes through the 
agency of fleas, ( Ceratophyllus fasciatus and Ctenopthalmus agyrtes). 
He believes that these insects are probably the chief transmitters 
of the parasite. He was also able to transmit it from diseased to 
healthy rats through the agency of the rat louse. He was unable 
to trace any developmental stages in the louse and inclined to the 
opinion that Prowazek was deceived by the presence of extraneous 
flagellates such as are known to exist in a number of blood-sucking 
arthropods. 

Nuttall concludes that since three distinct kinds of blood-sucking 
insects are capable of transmitting Trypanosoma lewisi it appears 


214 Arthropods as Essential Hosts of Pathogenic Protozoa 

doubtful that this flagellate is a parasite of the invertebrate “host” 
in the sense claimed by Prowazek and other investigators. 

Tsetse-flies and Nagana —One of the greatest factors in retarding 
the development of certain regions of Africa has been the presence 
of a small fly, little larger than the common house-fly. This is the 
tsetse-fly, Glossina morsitans (fig. 165) renowned on account of the 
supposed virulence of its bite for cattle, horses and other domestic 
mammals. 

The technical characteristics of the tsetse-flies, or Glossinas, and 
their several species, will be found in a later chapter. We need 
emphasize only that they are blood-sucking Muscidse and that, 
unlike the mosquitoes, the sexes resemble each other closely in struc¬ 
ture of the mouth-parts, and in feeding habits. 

In 1894, Colonel David Bruce discovered that the fly was not in 
itself poisonous but that the deadly effect of its bite was due to the 
fact that it transmitted a highly pathogenic blood parasite, Trypano¬ 
soma brucei. This trypanosome Bruce had discovered in the blood 
of South African cattle suffering from a highly fatal disease known as 
“nagana”. On inoculating the blood of infected cattle into horses 
and dogs he produced the disease and found the blood teeming with 
the causative organism. In the course of his work he established 
beyond question that the “nagana” and the tsetse-fly disease were 
identical. 

Tsetse-flies of the species Glossina morsitans, which fed upon 
diseased animals, were found capable of giving rise to the disease 
in healthy animals up 'to forty-eight hours after feeding. Wild 
tsetse-flies taken from an infected region to a region where they did 
not normally occur were able to transmit the disease to healthy 
animals. It was found that many of the wild animals in the tsetse- 
fly regions harbored Trypanosoma brucei in their blood, though they 
showed no evidence of disease. As in the case of natives of malarial 
districts, these animals acted as reservoirs of the parasite. Non- 
immune animals subjected to the attacks of the insect earner, quickly 
succumbed to the disease. 

A question of prime importance is as to whether the insect serves 
as an essential host of the pathogenic protozoan or whether it is a 
mere mechanical earner. Bruce inclined to the latter view. He was 
unable to find living trypanosomes in the intestines or excrements 
of the fly or to produce the disease on the many occasions when he 


Tsetse-flies and Nagana 


215 


injected the excrement into healthy animals. Moreover, he had 
found that the experimental flies were infective only during the first 
forty-eight hours and that if wild flies were taken from the infected 
region, “kept without food for three days and then fed on a healthy 
dog, they never gave rise to the disease.” 

Koch had early described what he regarded as sexual forms from 
the intestine of the fly but it remained for Kleine (1909) to experi¬ 
mentally demonstrate that a part of the life cycle of the parasite 
was undergone in the fly. Working with Glossina palpalis, he found 
that for a period of ten days or longer after feeding on an animal 
suffering from nagana it was non-infective, but that then it became 
infective and was able to transmit the disease for weeks thereafter. 
He discovered and described developmental stages of the parasite 
within the intestine of the insect. In other words, the tsetse-fly 
(in nature, Glossina morsitans), serves as an essential host, within 
which an important part of the life cycle of the parasite is undergone. 
These conclusions were quickly verified by Bruce and numerous 
other workers and are no longer open to question. Klein and Taute 
are even inclined to think that mechanical transmission plays practi¬ 
cally no role in nature, unless the fly is interrupted while feeding 
and passes immediately to a new animal. 

Tsetse-flies and Sleeping Sickness of Man— About the beginning 
of the present century a hitherto little known disease of man began 
to attract great attention on account of its ravages in Uganda and 
the region of Victoria Nyanza in South Africa. It was slow, insidu- 
ous and absolutely fatal, characterized in its later stages by dullness, 
apathy, and finally absolute lethargy all day long, symptoms which 
gave it the name of “sleeping sickness.” 

It was soon found that the disease was not a new one but that it 
had been known for over a hundred years on the west coast of Africa. 
Its introduction into Central and East Africa and its rapid spread 
have been attributed primarily to the development of the country, 
the formation of new trade routes and the free mingling of native 
tribes formerly isolated. It is estimated that in the first ten years 
of the present century there were approximately two hundred 
thousand deaths from the disease in the Uganda protectorate. In 
the British province Bugosa, on the Victoria Nyanza there were 
thirty thousand deaths in the period from 1902-1905. 


216 Arthropods as Essential Hosts of Pathogenic Protozoa 

While the disease is peculiarly African there are a number of 
instances of its accidental introduction into temperate regions. 
Slaves suffering from it were occasionally brought to America in 
the early part of the last century and cases have sometimes been 
imported into England. In none of the cases did the disease gain a 
foothold or spread at all to other individuals. 

In 1902 Dutton described a trypanosome, T. gamhiense, which he 
and Forde had found the year before in the blood of a patient suffer¬ 
ing from a peculair type of fever in Gambia. In 1902-1903 Castel- 
lani found the same parasite in the cerebro-spinal fluid of sleeping- 
sickness patients and definitely reported it as the causative organism 
of the disease. His work soon found abundant confirmation, and 
it was discovered that the sleeping sickness was but the ultimate 
phase of the fever discovered by Dutton and Forde. 

When Castellani made known his discovery- of the trypanosome 
of sleeping sickness, Brumpt, in France, and Sambon, in England, 
independently advanced the theory that the disease was transmitted 
by the tsetse-flv, Glossina palpalis. This theory was based upon the 
geographical distribution and epidemiology of the disease. Since 
then it has been abundantly verified by experimental evidence. 

Fortunately for the elucidation of problems relating to the methods 
of transfer of sleeping sickness, Trypanosoma gambiense is patho¬ 
genic for many species of animals. In monkeys it produces symptoms 
very similar to those caused in man. Bruce early showed that 
Glossina palpalis “fed on healthy monkeys eight, twelve, twenty-four 
and forty-eight hours after having fed on a native suffering from 
trypanosomiasis, invariably transmitted the disease. After three 
days the flies failed to transmit it.” In his summary in Osier’s 
Modem Medicine, he continues “But this is not the only proof that 
these flies can carry the infective agent. On the lake shore there 
was a large native population among whom we had found about 
one-third to be harboring trypanosomes in their blood. The tsetse- 
flies caught on this lake shore, brought to the laboratory in cages, 
and placed straightway on healthy monkeys, gave them the disease 
in every instance, and furnished a startling proof of the danger of 
loitering along the lake shore among those infected flies.” 

As in the case of nagana, Bruce and most of the earlier investi¬ 
gators supposed the transmission of the sleeping sickness trypano¬ 
some by Glossina palpalis to be purely mechanical. The work of 
Kleine (1909) clearly showed that for Trypanosoma gambiense as 


Tsetse-flies and Sleeping Sickness of Man 217 

well as for Trypanosoma brucei the fly served as an essential host. 
Indeed, Kleine and many subsequent investigators are inclined to 
think that there is practically no mechanical transmission of trypan¬ 
osomes from animal to animal by Glossina in nature, and that the 
many successful experiments of the earlier investigators were due 
to the fact that they used wild flies whkh already harbored the 
transformed parasite rather than directly inoculated it from the 
blood of the diseased experimental animals. While the criticism 
is applicable to some of the work, this extreme view is not fully 
justified by the evidence at hand. 

Kleine states (1912) that Glossina palpalis can no longer be 
regarded as the sole transmitter of sleeping sickness. Taute (1911) 
had shown that under experimental conditions Glossina morsitans 
was capable of transferring the disease and Kleine calls attention to 
the fact that in German East Africa, in the district of the Rovuma 
River, at least a dozen cases of the disease have occurred recently, 
though only Glossina morsitans exists in the district. It appears, 
however, that these cases are due to a different parasite, Trypano¬ 
soma rhodesiense. This species, found especially in north-east 
Rhodesia and in Nyassaland, is transferred by Glossina morsitans. 
y Other workers maintain that the disease may be transmitted by 
various blood-sucking flies, or even bugs and lice which attack man. 
Fullebom and Mayer (1907) have shown by conclusive experi¬ 
ments that Aedes ( Stegomyia ) calopus may transmit it from one 
animal to another if the two bites immediately succeed each other. 

It is not possible that insects other than the tsetse-flies (and only 
certain species of these), play an important role in the transmission 
of the disease, else it would be much more wide-spread. Sambon 
(1908) pointed out that the hypothesis that is spread by Aedes 
calopus is opposed by the fact that the disease never spread in the 
Antilles, though frequently imported there by West African slaves. 
The same observation would apply also to conditions in our own 
Southern States in the early part of the past century. 

Since Glossina palpalis acts as an essential host of the parasite 
and the chief, if not the only, transmitter, the fight against sleeping 
sickness, like that against malaria and yellow fever, becomes pri¬ 
marily a problem in economic entomology. The minutest detail 
of the life-history, biology, and habits of the fly, and of its parasites 
and other natural enemies becomes of importance in attempts to 
eradicate the disease. Here we can consider only the general features 
of the subject. 


2i8 Arthropods as Essential Hosts of Pathogenic Protozoa 

Glossina palpalis lives in limited areas, where the forest and under¬ 
growth is dense, along the lake shore or river banks. According to 
Hodges, the natural range from shore is under thirty yards, though 
the distance to which the flies may follow man greatly exceed this. 

It is a day feeder, a fact which may be taken advantage of in 
avoiding exposure to its attacks. The young are brought forth alive 
and full-grown, one every nine or ten days. Without feeding, they 
enter the ground and under favorable conditions, complete their 
development in a month or more. 



137. Sleeping sickness concentration camp in German East Africa. Report of German 
Commission. 


Methods of control of the disease must look to the prevention 
of infection of the flies, and to their avoidance and destruction. 
Along the first line, much was hoped from temporary segregation 
of the sick in regions where the fly was not found. On the assump¬ 
tion that the flies acted as carriers only during the first two or three 
days, it was supposed that even the “fly belts” would become safe 
within a few days after the sick were removed. The problem was 
found to be a much more difficult one when it was learned that after 
a given brief period the fly again became infective and remained so 
for an indeterminate period. Nevertheless, isolation of the sick 
is one of the most important measures in preventing the spread of 










South American Trypanosomiasis 


219 


the disease into new districts. Much, too, is being accomplished 
by moving native villages from the fly belts, (c.f. fig. 137.) 

All measures to avoid the flies should be adopted. This means 
locating and avoiding the fly belts as far as possible, careful screen¬ 
ing of houses, and protection of the body against bites. 

Clearing the jungle along the water courses for some yards beyond 
the natural range of the fly has proved a very important measure. 
Castellani recommends that the area be one hundred yards and 
around a village three hundred yards at least. 

Detailed studies of the parasites and the natural enemies of the 
tsetse-fly are being undertaken and may ultimately yield valuable 
results. 

South American Trypanosomiasis — The tsetse-flies are distinc¬ 
tively African in distribution and until recently there were no tryan- 
osomes known to infest man in America. In 1909 Dr. Chagas, of 
Rio de Janeiro described a new species, Trypanosoma cruzi, patho¬ 
genic to man. 

Trypanosoma cruzi is the causative organism of a disease common 
in some regions of Brazil, where it is known as “opilacao.” It is 
especially to be met with in children and is characterized by extreme 
anemia, wasting, and stunted development associated with fever, 
and enlargenemt of the thyroid glands. The disease is transmitted 
by the bites of several species of assassin-bugs, or Reduviidae, not¬ 
ably by Conorhinus megistus. The evolution of the parasite within 
the bug has been studied especially by Chagas and by Brumpt. 
From the latter’s text we take the following summary. 

The.adult tryanosomes, ingested by a Conorhinus megistus, of 
any stage, first change into Crithidia-hke forms and then those 
which remain in the stomach become ovoid and non-motile. Brumpt 
found these forms in immense numbers, in a Cornohinus which had 
been infested fourteen months before. The forms which pass into 
the intestine quickly assume the Crithidia form and continue to 
develop rapidly under this form. Some weeks later they evolve 
into the trypanosome forms, pathogenic for man. They then pass 
out with the excrement of the bug and infect the vertebrate host 
as soon as they come in contact with any mucous layer (buccal, 
ocular or rectal). More rarely they enter through the epidermis. 

Brumpt showed that the development could take place in three 
species; bed-bugs ( Cimex lectularius, C. hemipterus ) and in the tick 


220 Arthropods as Essential Hosts of Pathogenic Protozoa 

Ornithodoros moubata. The evolution proceeds in the first two 
species of bed-bugs as rapidly as in Conorhinus, or even more rapidly, 
but they remain infective for a much shorter time and hence Brumpt 
considers that they play a much less important role in the spread of 
the disease. 

Conorhinus megistus, like related forms in our Southern States, 
very commonly frequents houses and attacks man with avidity. 
Chagas states that the bites are painless and do not leave any traces. 
They are usually inflicted on the lips, or the cheeks and thus the 
buccal mucosa of a sleeper may be soiled by the dejections of the 
insect and the bite serving as a port of entry of the virus, remain 
unnoticed. 

The possibility of some of our North American Reduviidse play¬ 
ing a similar role in the transmission of disease should not be over¬ 
looked. 

Leishmanioses and Insects—Closely related to the trypanosomes 
is a group of intracellular parasites which have recently been grouped 
by Ross under the genus Leishmania. Five species are known to 
affect man. Three of these produce local skin infestations, but two 
of them, Leishmania donovani and L. infantum, produce serious and 
often fatal systemic diseases. 

The first of these, that produced by L. donovani, is an exceedingly 
virulent disease common in certain regions of India and China. It 
is commonly known as “Kala-azar,” or “dum-dum” fever, and more 
technically as tropical leishmaniasis. Patton (1907) believes that 
the parasite is transmitted by the bed-bug Cimex hemipterus, and has 
described a developmental cycle similar to that which can be found 
in artificial cultures. On the other hand, Donovan was unable to 
confirm Patton’s w r ork and believes that the true intermediate host is 
a Reduviid bug, Conorhinus rubrofasciatus. 

Leishmania infantum is the cause of the so-called infantile splenic 
leishmaniasis, occurring in northern Africa, Spain, Portugal, Italy, 
and possibly other parts of Europe. The parasite occurs habitually 
in the dog and is only accidentally transferred to children, Alvares 
and da Silva, in Portugal (according to Brumpt, 1913) have found 
that the excrement of a flea from a diseased dog contains flagellates, 
and they suggest that the infection may be transmitted by the acci¬ 
dental inoculation of this excrement by means of the proboscis of the 
flea, as has been thought to occur in the case of the plague. To this 


Leishmanioses and Insects 


221 


Brumpt objects that they and other workers who thought to trace 
the development of Leishmania infantum were apparently misled by 
the presence of a harmless Herpetomonas which infests dog fleas in all 
countries, even where the leishmaniasis is unknown. 

Basile (1910 and 1911) however, carried on numerous experiments 
indicating that the disease was transferred from children to dogs 
and from dog to dog by the dog flea, and was able to find in the 
tissues of the insects forms perfectly identical with those found in 
children and in dogs suffering from leishmaniasis. He also found 
that Pulex irritans was capable of acting as the carrier. 

Of the cutaneous type of leishmaniasis, the best known is the so- 
called “Oriental sore,” an ulcerative disease of the skin which is 
epidemic in many tropical and subtropical regions. The causative 
organism is Leishmania tropica, which occurs in the diseased tissues 
as bodies very similar to those found in the spleen in cases of 
kala-azar. The disease is readily inoculable and there is no doubt 
that it may be transferred from the open sores to abraded surfaces of 
a healthy individual by house-flies. It is also believed by a number 
of investigators that it may be transferred and directly inoculated 
by various blood-sucking insects. 

Ticks and Diseases of Man and Animals 

We have seen that the way to the discoveries of the relations of 
arthropods to disease was pointed out by the work of Leuckart and 
Melnikoff on the life cycle of Dipylidium, and of Fedtschenko and 
Manson on that of Filaria. They dealt with grosser forms, belonging 
to well-recognized parasitic groups. 

This was long before the role of any insect as a carrier of patho¬ 
genic micro-organisms had been established, and before the Protozoa 
were generally regarded as of importance in the causation of disease. 
The next important step was taken in 1889 when Smith and Kil- 
bourrie conclusively showed that the so-called Texas fever of cattle, 
in the United States, is due to an intracorpuscular blood parasite 
transmitted exclusively by a tick. This discovery, antedating by 
eight years the work on the relation of the mosquito to malaria, had a 
very great influence on subsequent studies along these lines. 

While much of the recent work has dealt with the true insects, 
or hexapods, it is now known that several of the most serious diseases 
of animals, and at least two important diseases of man are tick 
borne. These belong to the types known collectively as babesioses 
(or “ piroplasmoses”) , and spirochcetoses. 


222 Arthropods as Essential Hosts of Pathogenic Protozoa 

The term babesiosis is applied to a disease of man or animals 
which is caused by minute protozoan parasites of the genus Babesia, 
living in the red blood corpuscles. These parasites have usually been 
given the generic name Piroplasma and hence the type of disease 
which they cause is often referred to as “ piroplasmosis.” The best 
known illustration is the disease known in this country as Texas 
fever of cattle. 

Cattle Ticks and Texas Fever— The cattle disease, which in the 
United States is known as Texas fever, is a widely distributed, exceed¬ 
ingly acute disease. In Australia it is known as redwater fever and 
in Europe as haemoglobinuria, due to the fact that the urine of the 
diseased animals is discolored by the breaking down of the red blood 
corpuscles infested by the parasite. 

In their historical discussion, Smith and Kilbourne, point out that 
as far back as 1796 it was noted that Southern cattle, in a state of 
apparent health, might spread a fatal disease among Northern herds. 
As observations accumulated, it was learned that this infection was 
carried only during the warm season of the year and in the depth of 
winter Southern cattle were harmless. Moreover, Southern cattle 
after remaining for a short time in the North lost their power to 
transmit the disease, and the same was true of cattle which had been 
driven for a considerable distance. 

Very significant was the fact that the infection was not com¬ 
municated directly from the Southern to Northern cattle but that 
the ground over which the former passed was infected by them, and 
that the infection was transmitted thence to susceptible cattle after 
a period of not less than thirty days had elapsed. 

Of course a disease as striking as this, and which caused such 
enormous losses of cattle in the region invaded was fruitful in theories 
concerning its causation. The most widespread was the belief that 
pastures were infected by the saliva, urine, or manure of Southern 
cattle. There were not wanting keen observers who suggested that 
the disease was caused by ticks, but little weight was given to their 
view. 

Various workers had described bacteria which they had isolated 
from the organs of the diseased animals, but their findings could not 
be verified. In 1889, Smith and Kilbourne discovered a minute, 
pear-shaped organism (fig. 138) in the red blood corpuscles of a cow 
which had succumbed to Texas fever. On account of their shape 


Cattle Ticks and Texas Fever 


2 23 




OOOOO 


OOOO® 


138. 


Babesia bovis in blood corpuscles 
After Calli. 


they were given the generic name Pyrososma and because they were 
usually found two in a corpuscle, the specific name, bigeminum. It 

is now generally accepted that 
the parasite is the same which 
Babes had observed the year 
before in Roumanian cattle 
suffering from haemoglobinuria, 
and should be known as Babesia 
bovis (Babes). 

By a series of perfectly con¬ 
clusive experiments carried on 
near Washington, D. C., Smith 
and Kilboume showed that 
this organism was carried from Southern cattle to non-immune ani¬ 
mals by the so-called Southern cattle 
tick, Boophilus annulatus (= Mar- 
garopus annulatus) (fig. 139). 

Of fourteen head of native cattle 
placed in a field with tick-infested 
Northern cattle all but two contracted 
the disease. This experiment was 
repeated with similar results. Four 
head of native cattle kept in a plot 
with three North Carolina cattle 
which had been carefully freed from 
ticks remained healthy. A second 
experiment the same year gave similar 
results. 

Still more conclusive was the ex¬ 
periment showing that fields which a. 

had not been entered by Southern 
cattle but which had been infected by 
mature ticks taken from such animals 
would produce Texas fever in native 
cattle. On September 13, 1889, sev¬ 
eral thousand ticks collected from 
cattle in North Carolina three and 
four days before, were scattered in a 
small field near W ashington. Three 139 . Thecattietick(Boophiiusannuiatus). 
out of four native animals placed in comftoTk! 61 {b) ma!e ‘ Atter 








224 Arthropods as Essential Hosts of Pathogenic Protozoa 

this field contracted the disease. The fourth animal was not 
examined as to its blood but it showed no external symptoms of 
the disease. 

In these earlier experiments it was believed that the cattle tick 
acted as a carrier of the disease between the Southern cattle and the 
soil of the Northern pastimes. “It was believed that the tick ob¬ 
tained the parasite from the blood of its host and in its dissolution 
on the pasture a certain resistant spore form was set free which 
produced the disease when taken in with the food.” The feeding of 
one animal for some time with grass from the most abundantly 



140. Hyalomma aegypticum. After Nuttall and Warburton. 


infected field, without any appearance of the disease, made this 
hypothesis untenable. 

In the experimental work in 1890 the astonishing fact was brought 
out that the disease was conveyed neither by infected ticks dis¬ 
integrating nor by their directly transferring the parasite, but that 
it was conveyed by the young hatched from eggs of infected ticks. 
In other words, the disease was hereditarily transferred to ticks of 
the second generation and they alone were capable of conveying it. 

Thus was explained the fact that Texas fever did not appear 
immediately along the route of Southern cattle being driven to 
Northern markets but that after a certain definite period it mani¬ 
fested itself. It was conveyed by the progeny of ticks which had 
dropped from the Southern cattle and deposited their eggs on the 
ground. 





Cattle Ticks and Texas Fever 


225 


These results have been fully confirmed by workers in different 
parts of the world,—notably by Koch, in Africa, and by Pound, in 
Australia. 

The disease is apparently transmitted by Boopliilus annulatus 
alone, in the United States, but it, or an almost identical disease, 
is conveyed by Ixodes hexagonus in Norway, Ixodes ricinus in Finland 
and France and by the three species, Boophilus decoloratus , Hyalomma 
cegypticum (fig. 140 and 141), and Hcemaphysalis punctata in Africa. 

In spite of the detailed study which it has received, the life cycle 
of Babesia bovis has not been satisfactorily worked out. The asexual 

reproduction in the 
blood of the vertebrate 
host has been described 
but the cycle in the tick 
is practically unknown. 

More successful 
attempts have been 
made to work out the life 
cycle of a related species, 
Babesia canis, which 
causes malignant jaun¬ 
dice in dogs in Africa 
and parts of Southern 
Europe. In this in¬ 
stance, also, the disease 
is transmitted by heredity to the ticks of the second generation. 
Yet the larval, or “seed ticks,’’ from an infected female are not 
capable of conveying the disease, but only the nymphs and adults. 
Still more complicated is the condition in the case of Babesia ovis of 
sheep, which Motas has shown can be conveyed solely by the adult, 
sexually mature ticks of the second generation. 

In Babesis canis , Christopher (1907) observed developmental 
stages in the tick. He found in the stomach of adult ticks, large 
motile club-shaped bodies which he considered as ookinetes. These 
bodies pass to the ovaries of the tick and enter the eggs where they 
become globular in form and probably represent an oocyst. This 
breaks up into a number of sporoblasts which enter the tissues of 
the developing tick and give rise to numerous sporozoites, which 
collect in the salivary glands and thence are transferred to the 
vertebrate host. A number of other species of Babesia are known 




141. 


Hyalomma aegypticum. Capitulum of female; 
(a) dorsal, (6) ventral aspect. 










226 Arthropods as Essential Hosts of Pathogenic Protozoa 

to infest vertebrates and in all the cases where the method has been 
worked out it has been found that the conveyal was by ticks. We 
shall not consider the cases more fully here, as we are concerned 
especially with the method of transfer of human diseases. 

Ticks and Rocky Mountain Spotted Fever of Man — Ever since 
1873 there has been known in Montana and Idaho a peculiar febrile 
disease of man, which has gained the name of “Rocky Mountain 
spotted fever.” Its onset is marked by chills and fever which rapidly 
become acute. In about four to seven days there appears a charac¬ 
teristic eruption on the wrists, ankles or back, which quickly covers 
the body. 

McClintic (1912) states that the disease has now been reported 
from practically all of the Rocky Mountain States, including Arizona, 
California, Colorado, Idaho, Montana, Nevada, Oregon, Utah, 
Washington, and Wyoming. “Although the disease is far more 
prevalent in Montana and Idaho than in any of the other States, 
its spread has assumed such proportions in the last decade as to call 
for the gravest consideration on the part of both the state and national 
health authorities. In fact, the disease has so spread from state 
to state that it has undoubtedly become a very serious interstate 
problem demanding the institution of measures for its control and 
suppression.” 

A peculiar feature of the Rocky Mountain spotted fever is a 
marked variation in its severity in different localities. In Montana, 
and especially in the famous Bitter Root Valley, from 33 per cent to 
75 per cent of the cases result fatally. On the other hand, the fatality 
does not exceed four per cent in Idaho. 

In 1902, Wilson and Chowning reported the causative organism 
of spotted fever to be a blood parasite akin to the Babesia of Texas 
fever, and made the suggestion that the disease was tick-borne. 
The careful studies of Stiles (1905) failed to confirm the supposed 
discovery of the organism, and the disease is now generally classed 
as due to an invisible virus. On the other hand, the accumulated 
evidence has fully substantiated the hypothesis that it is tick-borne. 

According to Ricketts (1907) the experimental evidence in sup¬ 
port of this hypothesis was first afforded by Dr. L. P. McCalla and 
Dr. II. A. Brereton, in 1905. These investigators transmitted the 
disease from man to man in two experiments. “The tick was 
obtained ‘from the chest of a man very ill with spotted fever’ and 


Ticks and Rocky Mountain Spotted Fever of Man 227 

‘applied to the arm of a man who had been in the hospital for two 
months and a half, and had lost both feet from gangrene due to 
freezing.’ On the eighth day the patient became very ill and passed 
through a mild course of spotted fever, leaving a characteristic 
eruption. The experiment was repeated by placing the tick on a 
woman’s leg and she likewise was infected with spotted fever.” 

The most detailed studies were those of the late Dr. H. T. Ricketts, 
and it was he who clearly established the tick hypothesis. In the 
summer of 1906 he found that guinea pigs and monkeys are very 
susceptible to spotted fever and can readily be infected by inocula¬ 
tion of blood from patients suffering from the disease. This opened 
the way to experimental work on tick transmission. A female tick 
was fed upon an infected guinea pig for two days, removed and 
isolated for two days and then placed upon a healthy guinea pig. 
After an incubation period of three and a half days the experimental 
animal contracted a well-marked case of the disease. 

A similar result was obtained at the same time by King, and later 
in the season Ricketts proved that the male tick was also capable 
of transmitting the disease. He found that there was a very inti¬ 
mate relation of the virus to the tick and that the transmission must 
be regarded as biological throughout. Ticks remained infective as 
long as they lived and would feed for a period of several months. If 
they acquired the disease in the larval or nymphal stage they retained 
it during molting and were infective in the subsequent stages. In a 
few cases the larvae from an infected female were infective. 

The evidence indicated that the tick suffers from a relatively 
harmless, generalized infection and the virus proliferates in its 
body. The disease probably is transferred through the salivary 
secretion of the tick since inoculation experiments show that the 
salivary glands of the infected adult contain the virus. 

It is probable that in nature the reservoir of the virus of spotted 
fever is some one or more of the native small animals. Infected 
ticks have been found in nature, and as various wild animals are 
susceptible to the disease, it is obvious that it may exist among them 
unnoticed. Wilson and Cdowning suggested that the ground squir¬ 
rel plays the principal role. 

Unfortunately, much confusion exists regarding the correct 
name of the tick which normally conveys the disease. In the medi¬ 
cal literature it is usually referred to as Dermacentor occidentalis, 
but students of the group now agree that it is specifically distinct. 


228 Arthropods as Essential Hosts of Pathogenic Protozoa 

Banks has designated it as Dermacentor vennstus and this name is 
used in the publications of the Bureau of Entomology. On the other 
hand, Stiles maintains that the common tick of the Bitter Root 
Valley, and the form which has been collected by the authors who 
have worked on Rocky Mountain spotted fever in that region, is 
separable from D. venustus, and he has described it under the name of 
Dermacentor andersoni. 

Maver (1911) has shown experimentally that spotted fever may 
be transmitted by several different species of ticks, notably Dermacen¬ 
tor marginatus , Dermacentor variahilis and Amblyomma americanum. 
This being the case, the question of the exact systematic status of 
the species experimented upon in the Bitter Root Valley becomes 
less important, for since Dermacentor occidentalis, Dermacentor 
venustus and Dermacentor andersoni all readily attack man, it is 
probable that either species would readily disseminate the disease 
if it should spread into their range. 

Hunter and Bishop (1911) have emphasized the fact that in the 
eastern and southern United States there occur several species which 
attack man, and any one of which might transmit the disease from 
animal to animal and from animal to man. The following species, 
they state, would probably be of principal importance in the Southern 
and Eastern States: the lone star tick ( Amblyomma americanum)] 
the American dog tick ( Dermacentor variabilis) ; and the gulf-coast 
tick ( Amblyomma maculatum). In the extreme southern portions of 
Texas, Amblyomma cajennense, is a common pest of man. 

Since the evidence all indicates that Rocky Mountain spotted 
fever is transmitted solely by the tick, and that some of the wild 
animals serve as reservoirs of the virus, it is obvious that personal 
prophylaxis consists in avoiding the ticks as fully as possible, and in 
quickly removing those which do attack. General measures along 
the line of tick eradication must be carried out if the disease is to be 
controlled. That such measures are feasible has been shown by the 
work which has been done in controlling the tick-borne Texas fever 
of cattle, and by such work as has already been done against the 
spotted fever tick, which occurs on both wild and domestic animals. 
Detailed consideration of these measures is to be found in the 
publications of the Public Health and Marine Hospital Service, 
and the Bureau of Entomology. Hunter and Bishopp give the 
following summarized recommendations for control or eradication 
measures in the Bitter Root Valley. 


Ticks and Rocky Mountain Spotted Fever of Man 229 

(1) A campaign of education, whereby all the residents of the 
valley will be made thoroughly familiar with the feasibility of the 
plan of eradication, and with what it will mean in the development of 
the valley. 

(2) The obtaining of legislation to make it possible to dip or oil 
all live stock in the Bitter Root Valley. 

(3) The obtaining of an accurate census of the horses, cattle, 
sheep, mules, and dogs in the valley. 

(4) The construction of ten or more dipping vats. 

(5) The providing of materials to be used in the dipping mixture. 

(6) The organization of a corps of workers to carry on the opera¬ 
tions. 

(7) The systematic dipping of the horses, cattle, sheep, and dogs 
of the valley on a definite weekly schedule from approximately March 
10 to June 9. 

(8) The treatment by hand of the animals in localities remote 
from vats, on the same schedule. 

They estimate that after three seasons’ operations a very small 
annual expenditure would provide against reinfestation of the valley 
by the incoming of cattle from other places. 

Supplementary measures consist in the killing of wild mammals 
which may harbor the tick; systematic burning of the brush and 
debris on the mountain side; and in clearing, since the tick is seldom 
found on land under cultivation. 


CHAPTER X 


ARTHROPODS AS ESSENTIAL HOSTS OF PATHOGENIC PROTOZOA 

[Continued] 

Arthropods and Spiroch.etoses of Man and Animals 

The term spiroehaetoses is applied to diseases of man or animals 
which are due to protistan parasites belonging to the group of slender, 
spiral organisms known as spirochaetes. 

There has been much discussion concerning the relationship of 
the spirochaetes. Formerly, they were regarded as bacteria closely 
related to the forms grouped in the genus Spirillum. The results 
of the detailed study which the spirochaetes have received in 
recent years, have led most of the workers to consider them as belong¬ 
ing to the protozoa. The merits of the discussion we are not con¬ 
cerned with here, but rather with the fact that a number of diseases 
caused by spirochaetes are arthropod-borne. The better known of 
these we shall discuss. 

African Relapsing Fever of Man —It has long been known to the 
natives of Africa and to travelers in that country, that the bite of a 
certain tick, Ornithodoros moubata, may be followed by severe or 
even fatal fever of the relapsing type. Until recent years, it was 
supposed that the effect was due to some special virulence of the tick, 
just as nagana of cattle was attributed to the direct effect of the bite 
of the tsetse-flv. The disease is commonly known as “tick-fever” 
or by the various native names of the tick. 

In 1904, Ross and Milne, in Uganda, and Dutton and Todd on the 
Congo, discovered that the cause of the disease is a spirochsete which 
is transmitted by the tick. This organism has been designated by 
Novy and Knapp as Spiroclueta duttoni. 

Ornithodoros moubata (fig. 142), the carrier of African relapsing 
fever, or “tick-fever,” is widely distributed in tropical Africa, and 
occurs in great numbers in the huts of natives, in the dust, cracks 
and crevices of the dirt floors, or the walls. It feeds voraciously 
on man as well as upon birds and mammals. Like others of the 
Argasidce, it resembles the bed-bug in its habit of feeding primarily 
at night. Dutton and Todd observed that the larval stage is under¬ 
gone in the egg and that the first free stage is that of the octopod 
nymph. 


230 


African Relapsing Fever of Man 


231 



142. Ornithodoros moubata. (a) Anterior part of venter; ( b) second stage 
nymph; (c) capitulum; ( d) dorsal and ( e) ventral aspect of female; 
(/) ventral aspect of nymph; (g) capitulum of nymph. After Nuttall 
and Warburton. 









232 Arthropods as Essential Hosts of Pathogenic Protozoa 

The evidence that the fever is transmitted by this tick is con¬ 
clusive. Koch found that from five per cent to fifteen per cent, and 
in some places, fifty per cent of the ticks captured, harbored the 
spirochaete. The disease is readily transmitted to monkeys, rats, 
mice and other animals and the earlier experiments along these lines 
have been confirmed by many workers. 

Not only are the ticks which have fed on infected individuals 
capable of conveying the disease to healthy animals but they trans¬ 
mit the causative organism to their progeny. Thus Mollers (1907), 
working in Berlin, repeatedly infected monkeys through the bites 
of nymphs which had been bred in the laboratory from infected ticks. 
Still more astonishing was his discovery that ticks of the third genera¬ 
tion were infective. In other words, if the progeny of infected ticks 
were fed throughout life on healthy animals, and on maturity de¬ 
posited eggs, the nymphs which hatched from these eggs would still 
be capable of carrying the infection. 

The developmental cycle of the spirochaete within the tick has not 
been fully worked out, though the general conclusions of Leishman 
(1910) have been supported by the recent works of Balfour (1911 
and 1912), and Hindle (1912), on the life cycle of spirochaetes affect¬ 
ing fowls. 

Spirochceta duttoni ingested by Ornithodoros moubata apparently 
disappear within a few days, but Leishman believed that in reality 
they break up into minute granules which are to be found in the 
alimentary canal, the salivary glands and the Malpighian tubes of 
the tick. These granules, or “coccoid bodies,” as Hindle calls them, 
are supposed to be the form in which the spirochaetes infect the new 
host. We shall see later that Marchoux and Couvy (1913) dis¬ 
sent wholly from this interpretation. 

According to Leishman, and Hindle, the coccoid bodies are not 
injected into the vertebrate host with the saliva of the tick, as are 
the sporozoites of malaria with that of the mosquito. Instead, they 
pass out with the excrement and secondarily gain access to the 
wound inflicted by the tick. 

Nuttall (1912) calls attention to the fact that the geographical 
distribution of Ornithodoros moubata is far wider than our present 
records show for the distribution of the relapsing fever in man and 
that there is every reason to fear the extension of the disease. Huts 
where the ticks occur should be avoided and it should be remembered 
that in infected localities there is special danger in sleeping on the 
ground. 


European Relapsing Fever 


233 


European Relapsing Fever —There is widely distributed in Europe 
a type of relapsing fever which is caused by Spirochceta recurrentis. 
It has long been supposed that this disease is spread by the bed-bug 
and there is some experimental evidence to show that it may be 
conveyed by these insects. 

In 1897, Tictin found that he could infect monkeys by inoculating 
the contents of bed-bugs which had fed upon a patient within forty- 
eight hours. Nuttall, in 1907, in one experiment succeeded in trans¬ 
mitting Spirochceta recurrentis from mouse to mouse by bites of bed¬ 
bugs. The bugs, thirty-five in number, were transferred at short 
intervals from one mouse to another, not being allowed to take a 
full meal on the first, or infected mouse. 

On the other hand, there is much clinical evidence to show that 
the European relapsing fever like various other types of the disease 
is transmitted from man to man by head and body lice ( Pediculus 
humanus and Pediculus corporis). 

Interesting supplementary evidence is that of Bayon’s observa¬ 
tions (1912), in Moscow. ‘ ‘ Having visited the big municipal night hos- 
pitals at Moscow I soon noticed that they were kept with such scrupu¬ 
lous cleanliness, disinfected so lavishly, the beds of iron, the floor cement¬ 
ed, that it was not possible for bed-bugs to thrive to any extent on 
the premises. The people sleeping there were allowed, however, 
to sleep in their own clothes. The introduction of these model homes 
had not had any effect on the incidence of relapsing fever, for the 
places were still hot-beds of the fever during winter. On the other 
hand, though I changed my rooms several times, I found bugs in 
every successive lodging, and I was told in Moscow, this can hardly 
be avoided. Yet no foreigner, or Russian of the better class, ever 
catches relapsing fever. To this may be added the fact that when 
I asked for clothes-lice and promised to pay a kopec for two, the 
attendants from the night hostel brought me next morning a small 
ounce bottle crammed with Pediculus capitis (= P. humanus), and 
Pediculus vestimentorum (= P. corporis) collected off the sleepers. 
If relapsing fever were transmitted by bed-bugs, it would be much 
more disseminated than it is at present in Moscow.” 

Direct experimental evidence of the agency of lice in transmitting 
relapsing fever is especially clear in the case of a type of the disease 
prevalent in parts of North Africa. We shall consider this evidence 
later. 


234 Arthropods as Essential Hosts of Pathogenic Protozoa 

Other Types of Relapsing Fever of Man —In addition to the three 
types of human relapsing fever already referred to, several others 
have been distinguished and have been attributed to distinct species 
of spirochastes. The various spirochastoses of man are: 

African, caused by 5 . duttoni; European, caused by 5 . recur- 
rentis; North African, caused by 5 . berbera; East African, caused 
by 5 . rossi; East Indian, caused by 5 . carteri; North American, 
caused by 5 . novyi; South American, caused by 5 . duttoni {?) 

Nuttall (1912) in his valuable resume of the subject, has em¬ 
phasized that “in view of the morphological similarity of the sup¬ 
posedly different species of spirochaetes and their individual variations 
in virulence, we may well doubt if any of the ‘species’ are valid. 
As I pointed out four years ago, the various specific names given to 
the spirochaetes causing relapsing fever in man may be used merely 
for convenience to distinguish strains or races of different origin. 
They cannot be regarded as valid names, in the sense of scientific 
nomenclature, for virulence and immunity reactions are not adequate 
tests of specificity.” 

North African Relapsing Fever of Man -The type of human 
relapsing fever to be met with in Algeria, Tunis, and Tripoli, is due to 
a Spirochceta which does not differ morphologically from Spirochceta 
duttoni, but which has been separated on biological grounds as 
Spirochceta berberi. 

Experimenting with this type of disease in Algeria, Sergent and 
Foly (1910), twice succeeded in transmitting it from man to monkeys 
by inoculation of crushed body lice and in two cases obtained infec¬ 
tion of human subjects who had received infected lice under their 
clothing and who slept under coverings harboring many of the lice 
which had fed upon a patient. Their results were negative with 
Argas persicus, Cimex lectularius, Musca domestica, Hcematopinus 
spinulosus and Ceratophyllus fasciatus. They found body lice 
associated with every case of relapsing fever which they found in 
Algeria. 

Nicolle, Blaizot, and Conscil (1912) showed that the louse did 
not transmit the parasite by its bite. Two or three hours after it 
has fed on a patient, the spirochaetes begin to break up and finally 
they disappear, so that after a day, repeated examinations fail to 
reveal them. They persist, nevertheless, in some unknown form, 
for if the observations are continued they reappear in eight to twelve 


Spirochcetosis of Fowls 


235 


days. These new forms are virulent, for a monkey was infected 
by inoculating a single crushed louse which had fed on infected blood 
fifteen days before. 

Natural infection is indirect. Those attacked by the insect 
scratch, and in this act they excoriate the skin, crush the lice and 
contaminate their fingers. The least abrasion of the skin serves for 
the entrance of the spirochastes. Even the contact of the soiled 
fingers on the various mucosa, such as the conjunctive of the eye, 
is sufficient. 

As in the ease of Spirocheeta duttoni, the organism is transmitted 
hereditarily in the arthropod vector. The progeny of lice which 
have fed on infected blood may themselves be infective. 

Spirochaetosis of Fowls —One of the best known of the spirochaetes 
transmitted by arthropods is Spirocheeta gallinarum, the cause of a 
very fatal disease of domestic fowls in widely separated regions of 
the world. According to Nuttall, it occurs in Southeastern Europe, 
Asia, Africa, South America and Australia. 

In 1903, Marchoux and Salimbeni, working in Brazil, made the 
first detailed study of the disease, and showed that the causative 
organism is transmitted from fowl to fowl by the tick Argas persicus. 
They found that the ticks remained infective for at least five months. 
Specimens which had fed upon diseased birds in Brazil were sent to 
Nuttall and he promptly confirmed the experiments. Since that 
date many investigators, notably Balfour and Kindle, have contri¬ 
buted to the elucidating of the life-cycle of the parasite. Since it 
has been worked out more fully than has that of any of the human 
spirochaetes, we present Hindle’s diagram (fig. 143) and quote the 
brief summary from his preliminary paper (19116). 

“Commencing with the ordinary parasite in the blood of the fowl, 
the spirochaete grows until it reaches a certain length (16—1991.) and 
then divides by transverse division. This process is repeated, and 
is probably the only method of multiplication of the parasite within 
the blood. When the spirochaetes disappear from the circulation, 
some of them break up into the coccoid bodies which, however, 
do not usually develop in the fowl. When the spirochaetes are 
ingested by Argas persicus, some of them pass through the gut wall 
into the coelomic fluid. From this medium they bore their way into 
the cells of the various organs of the tick and there break up into a 
number of coccoid bodies. These intracellular forms multiply by 


236 Arthropods as Essential Hosts of Pathogenic Protozoa 

ordinary fission in the cells of the Malpighian tubules and gonads. 
Some of the coccoid bodies are formed in the lumen of the gut and 
Malpighian tubules. The result is that some of the coccoid bodies 
may be present in the Malpighian secretion and excrement of an 
infected tick and when mixed with the coxal fluid may gain entry 
into another fowl by the open wound caused by the tick’s bite. They 



then elongate and redevelop into ordinary spirochastes in the blood 
of the fowl, and the cycle may be repeated. 

Hindle’s account is clear cut and circumstantial, and is quite in 
line with the work of Balfour, and of Leishman. Radically different 
is the interpretation of Marchoux and Couvy (1913). These investi¬ 
gators maintain that the granules localized in the Malpighian tubules 
in the larvae and, in the adult, also in the ovules and the genital ducts 
of the male and female, are not derivod from spirochaetes but that they 
exist normally in many acariens. They interpret the supposed 







Typhus Fever and Pediculidce 


237 


disassoeiation of the spirochsete into granules as simply the first 
phase, not of a process of multiplication, but of a degeneration 
ending in the death of the parasite. The fragmented chromatin 
has lost its affinity for stains, remaining always paler than that of 
the normal spirochastes. On the other hand, the granules of Leish- 
man stain energetically with all the basic stains. 

Further, according to Marchoux and Couvy, infection takes 
place without the emission of the coxal fluid and indeed, soiling of the 
host by the coxal fluid diluting the excrement is exceptional. All 
of the organs of the Argasid are invaded by the parasites, but they 
pass from the coelom into the acini of the salivary glands and collect 
in its efferent canal. The saliva serves as the vehicle of infection. 

Thus, the question of the life cycle of Spirochceta gallinarum , and 
of spirochsetes in general, is an open one. 

It should be noted that Argas persicus, the carrier of Spirochceta 
gallinarum, is a common pest of poultry in the southwestern United 
States. Though the disease has not been reported from this counting 
conditions are such that if accidentally introduced, it might do great 
damage. 

Other Spirochaete Diseases of Animals About a score of other 
blood inhabiting spirochastes have been reported as occurring in 
mammals, but little is known concerning their life-histories. One 
of the most important is Spirochceta theileri which produces a spiro- 
chastosis of cattle in the Transvaal. Theiler has determined that it 
is transmitted by an Ixodid tick, Margaropus decoloratus. 

Typhus Fever and Pediculidce 

Typhus is an acute, and continued fever, formerly epidemically 
prevalent in camps, hospitals, jails, and similar places where persons 
were crowded together under insanitary conditions. It is accom¬ 
panied by a characteristic rash, which gives the disease the common 
name of “spotted” or “lenticular” fever. The causative organism 
is unknown. 

Typhus fever has not generally been supposed to occur in the 
United States, but there have been a few outbreaks and sporadic 
cases recognized. According to Anderson and Goldberger (1912a), 
it has been a subject of speculation among health authorities why, 
in spite of the arrival of occasional cases in this country and of many 
persons from endemic foci of the disease, typhus fever apparently 
does not gain a foothold in the United States. These same workers 


238 Arthropods as Essential Hosts of Pathogenic Protozoa 

showed that the so-called Brill’s disease, studied especially in New 
York City, is identical with the typhus fever of Mexico and of 
Europe. 

The conditions under which the disease occurs and under which 
it spreads most rapidly are such as to suggest that it is carried by 
some parasitic insect. On epidemiological grounds the insects most 
open to suspicion are the lice, bed-bugs and fleas. 

In 1909, Nicolle, Comte and Conseil, succeeded in transmitting 
typhus fever from infected to healthy monkeys by means of the 
body louse ( Pediculus corporis). Independently of this work, 
Anderson and Goldberger had undertaken work along this line in 
Mexico, and in 1910 reported two attempts to transmit the disease 
to monkeys by means of body lice. The first experiment resulted 
negatively, but the second resulted in a slight rise in temperature, 
and in view of later results it seems that this was due to infection 
with typhus. 

Shortly after, Ricketts and Wilder (1910) succeeded in transmitt¬ 
ing the disease to the monkey by the bite of body lice in two experi¬ 
ments, the lice in one instance deriving their infection from a man 
and in another from the monkey. Another monkey was infected 
by typhus through the introduction of the feces and abdominal 
contents of infested lice into small incisions. Experiments with 
fleas and bed-bugs resulted negatively. 

Subsequently, Goldberger and Anderson (19126) indicated that 
the head louse ( Pediculus humanus ) as well, may become infected 
with typhus. In an attempt to transmit typhus fever (Mexican 
virus) from man to monkey by subcutaneous injection of a saline 
suspension of crushed head lice, the monkeys developed a typical 
febrile reaction with subsequent resistance to an inoculation of 
virulent typhus (Mexican) blood. In one of the three experiments 
to transmit the disease from man to monkey by means of the bite 
of the head louse, the animal bitten by the presumably infected head 
lice proved resistant to two successive immunity tests with viru¬ 
lent typhus blood. 

In 1910, Ricketts and Wilder reported an experiment undertaken 
with a view to determining whether the young of infected lice were 
themselves infected. Young lice were reared to maturity on the 
bodies of typhus patients, so that if the eggs were susceptible to 
infection at any stage of their development, they would have every 
opportunity of being infected within the ovary. The eggs of these 
infected lice were obtained, they were incubated, and the young lice 


Typhus Fever and Pediculidce 


239 


of the second generation were placed on a normal rhesus monkey. 
The experimenters were unable to keep the monkey under very 
close observation during the following three or four weeks, but from 
the fact that he proved resistant to a subsequent immunity test 
they concluded that he probably owed this immunity to infection 
by these lice of the second generation. 

Anderson and Goldberger (19126) object that due consideration 
was not given to the possibility of a variable susceptibility of the 
monkey to typhus. Their similar experiment was “frankly nega¬ 
tive.” 

Prophylaxis against typhus fever is, therefore, primarily a ques¬ 
tion of vermin extermination. A brief article by Dr. Goldberger 
(1914) so clearly shows the practical application of his work and that 
of the other investigators of the subject, that we abstract from it 
the following account: 

“ In general terms it may be stated that association with a case of 
typhus fever in the absence of the transmitting insect is no more 
dangerous than is association with a case of yellow fever in the 
absence of the yellow fever mosquito. Danger threatens only when 
the insect appears on the scene.” 

“We may say, therefore, that to prevent infection of the indi¬ 
vidual it is necessary for him only to avoid being bitten by the louse. 
In theory this may readily be done, for we know that the body louse 
infests and attaches itself almost entirely to the body linen, and that 
boiling kills this insect and its eggs. Individual prophylaxis is 
based essentially, therefore, on the avoidance of contact with indi¬ 
viduals likely to harbor lice. Practically, however, this is not 
always as easy as it may seem, especially under the conditions of 
such intimate association as is imposed by urban life. Particularly 
is this the case in places such as some ol the large Mexican cities, 
where a large proportion of the population harbors this vermin. 
Under such circumstances it is well to avoid crowds or crowded places, 
such as public markets, crowded streets, or public assemblies at 
which the ‘peon’ gathers.” 

“Community prophylaxis efficiently and intelligently carried out 
is, from a certain point of view, probably easier and more effective 
in protecting the individual than is the individual’s own effort to 
guard himself. Typhus emphasizes, perhaps better than any other 
disease, the fact that fundamentally, sanitation and health are 
economic problems. In proportion as the economic condition of the 
masses has improved — that is, in proportion as they could afford 


240 Arthropods as Essential Hosts of Pathogenic Protozoa 

to keep clean-—the notorious filth disease has decreased or dis¬ 
appeared. In localities where it still prevails, its further reduction 
or complete eradication waits on a further improvement in, or exten¬ 
sion of, the improved economic status of those afflicted. Economic 
evolution is very slow process, and, while doing what we can to hasten 
it, we must take such precautions as existing conditions permit, 
looking to a reduction in or complete eradication of the disease.” 

“When possible, public bath houses and public wash houses, 
where the poor may bathe and do their washings at a minimum or 
without cost, should be provided. Similar provision should be 
made in military and construction camps. Troops in the field should 
be given the opportunity as frequently as possible to wash and scald 
or boil their body linen.” 

“Lodging houses, cheap boarding houses, night shelters, hospitals, 
jails and prisons, are important factors in the spread and frequently 
constitute foci of the disease. They should receive rigid sanitary 
supervision, including the enforcement of measures to free all inmates 
of such institutions of lice on admission.” 

“So far as individual foci of the disease are concerned these 
should be dealt with by segregating and keeping under observation 
all exposed individuals for 14 days—the period of incubation—from 
the last exposure, by disinfecting (boiling or steaming) the suspected 
bedding, body linen, and clothes, for the destruction of any possible 
vermin that they may harbor, and by fumigating (with sulphur) 
the quarters that they may have occupied.” 

“It will be noted that nothing has been said as to the disposition 
of the patient. So far as the patient is concerned, he should be 
removed to ‘clean’ surroundings, making sure that he does not 
take with him any vermin. This may be done by bathing, treating 
the hair with an insecticide (coal oil, tincture of larkspur), and a 
complete change of body linen. Aside from this, the patient may 
be treated or cared for in a general hospital ward or in a private house, 
provided the sanitary officer is satisfied that the new surroundings 
to which the patient has been removed are ‘clean,’ that is, free 
from vermin. Indeed, it is reasonably safe to permit a ‘clean’ 
patient to remain in his own home if this is ‘clean,’ for, as has al¬ 
ready been emphasized, there can be no spread in the absence of lice. 
This is a common experience in native families of the better class 
and of Europeans in Mexico City.” 

“Similarly the sulphur fumigation above prescribed may be 
dispensed with as unnecessary in this class of cases.” 


CHAPTER XI 


SOME POSSIBLE, BUT IMPERFECTLY ESTABLISHED CASES OF 
ARTHROPOD TRANSMISSION OF DISEASE 

Infantile Paralysis or Acute Anterior Poliomyelitis 

The disease usually known in this country as infantile paralysis 
or, more technically, as acute anterior poliomyelitis, is one which 
has aroused much attention in recent years. 

The causative organism of infantile paralysis is unknown, but 
it has been demonstrated that it belongs to the group of filterable 
viruses. It gives rise to a general infection, producing characteristic 
lesions in the central nervous system. The result of the injury to 
the motor nerves is a more or less complete paralysis of the corres¬ 
ponding muscle. This usually manifests itself in the legs and arms. 
The fatal cases are usually the result of paralysis of the muscles 
of respiration. Of the non-fatal cases about 60 per cent remain 
permanently crippled in varying degrees. 

Though long known, it was not until about 1890 that it was 
emphasized that the disease occurs in epidemic form. At this time 
Medin reported his observations on an epidemic of forty-three cases 
which occurred in and around Stockholm in 1887. Since then, 
according to Frost (1911), epidemics have been observed with increas¬ 
ing frequency in various parts of the world. The largest recorded 
epidemics have been those in Vermont, 1894, 126 cases; Norway and 
Sweden, 1905, about 1,500 cases; New York City, 1907, about 
2,500 cases. Since 1907 many epidemics have been reported in the 
United States, and especially in the Northern States east of the 
Dakotas. In 1912 there were over 300 cases of the disease in Buffalo, 
N. Y., with a mortality of somewhat over 11 per cent. 

In view of the sudden prominence and the alarming spread of 
infantile paralysis, there have been many attempts to determine 
the cause, and the manner in which the disease spreads and develops 
in epidemic form. In the course of these studies, the question of 
possible transmission by insects was naturally suggested. 

C. W. Howard and Clark (1912) presented the results of studies 
in this phase of the subject. They dealt especially with the house¬ 
fly, bedbug, head, and body lice, and mosquitoes. It was found 
that the house-fly {Musea domestica) can carry the virus of poliomye¬ 
litis in an active state for several days upon the surface of the body 

241 


242 Arthropod Transmission of Disease 

and for several hours within the gastro-intestinal tract. Mosquitoes 
and lice were found not to take up or maintain the virus. On the 
other hand, the bedbug ( Cimex lectularius) was found to take the 
virus from the infected monkeys and to maintain it in a living state 
within the body for a period of seven days. This was demonstrated 
by grinding up in salt solution, insects which had fed on poliomyeletic 
animals and injecting the filtrate into a healthy monkey. The experi¬ 
menters doubted that the bedbug is a carrier of the virus in nature. 

Earlier in the same year, Braes and Sheppard published the results 
of an intensive epidemiological study of the outbreak of 1911, in 
Massachusetts. Special attention had been paid to the possibility 
of insect transfer and the following conclusion was reached: 

“Field work during the past summer together with a consideration 
of the epidemiology of the disease so far as known, points strongly 
toward biting flies as possible carriers of the virus. It seems probable 
that the common stable-fly ( Stomoxys calcitrans L.) may be responsi¬ 
ble to a certain extent for the spread of acute epidemic poliomyelitis, 
possibly aided by other biting flies, such as Tabanus lineola. No 
facts which disprove such a hypothesis have as yet been adduced, 
and experiments based upon it are now in progress.” 

As stated by Braes (1913), especial suspicion fell upon the stable- 
fly because: 

1. The blood-sucking habits of the adult fly suit it for the transfer 
of virus present in the blood. 

2. The seasonal abundance of the fly is very closely correlated 
with the incidence of the disease, rising rapidly during the summer 
and reaching a maximum in July and August, then slowly declining 
in September and October. 

3. The geographical distribution of the fly is, so far as can be 
ascertained, wider, or at least eo-extensive with that of poliomyelitis. 

4. Stomoxys is distinctly more abundant under rural conditions, 
than in cities and thickly populated areas. 

5. While the disease spreads over districts quickly and in a 
rather erratic way, it often appears to follow along lines of travel, 
and it is known that Stomoxys flies will often follow horses for long 
distances along highways. 

6. In a surprisingly large number of cases, it appeared probable 
that the children affected had been in the habit of frequenting places 
where Stomoxys is particularly abundant, i.e., about stables, barn¬ 
yards, etc. 


Infantile Paralysis or Acute Anterior Poliomyelites 243 

The experiments referred to were earned on during the summer of 
1912 and in September Dr. Rosenau announced that the disease was 
transferred by the bite of the stable-fly. 

A monkey infected by inoculation was exposed to the bites of 
upwards of a thousand of the Stomoxys flies daily, by stretching it 
at full length and rolling it in a piece of chicken wire, and then placing 
it on the floor of the cage in which the flies were confined. The flies 
fed freely from the first, as well as later, after paralysis had set in. 
Alternating with the inoculated monkey, healthy monkeys were 
similarly introduced into the cage at intervals. New monkeys were 
inoculated to keep a supply of such infected animals and additional 
healthy ones were exposed to the flies, which fed willingly and in 
considerable numbers on each occasion. “Thus the flies were given 
every opportunity to obtain infection from the monkeys, since the 
animals were bitten during practically every stage of the disease 
from the time of the inoculation of the virus till their death follow¬ 
ing the appearance of paralysis. By the same arrangement the 
healthy monkeys were likely to be bitten by flies that had previously 
fed during the various stages of the disease on the infected monkeys. 
The flies had meanwhile enjoyed the opportunity of incubating the 
virus for periods varying from the day or two which usually elapses 
between consecutive feedings, to the two or three-week period for 
which at least some (although a very small percentage) of the flies 
lived in the cage.” 

“In all, twelve apparently healthy monkeys of a small Japan 
species were exposed to the flies in the manner described for the in¬ 
fected monkeys. Some were placed in the cage only once or twice 
and others a number of times after varying intervals. These ex¬ 
posures usually lasted for about half an hour, but were sometimes 
more protracted. No results were apparent until two or three 
weeks after the experiment was well under way, and then in rather 
rapid succession six of the animals developed symptoms of poliomye¬ 
litis. In three, the disease appeared in a virulent form, resulting 
in death, while the other three experienced transient tremblings, 
diarrhoea, partial paralysis and recovery.” — Brues, 1913. 

Very soon after the announcement of the results of experiments 
by Rosenau and Brues, they were apparently conclusively confirmed 
by Anderson and Frost (1912), who repeated the experiments, at 
Washington. They announced that through the bites of the Stomoxys 
flies that had previously fed on infected monkeys, they had succeeded 
in experimentally infecting three healthy monkeys. 


244 


Arthropod Transmission of Disease 


The results of these experiments gained much publicity and in 
spite of the conservative manner in which they had been announced, 
it was widely proclaimed that infantile paralysis was conveyed in 
nature by the stable-fly and by it alone. 

Serious doubt was cast on this theory by the results of further 
experiments by Anderson and Frost, reported in May of 1913. 
Contrary to the expectations justified by their first experience, the 
results of all the later, and more extended, experiments were wholly 
negative. Not once were these investigators again able to transmit 
the infection of poliomyelitis through Stomoxys. They concluded that 
it was extremely doubtful that the insect was an important factor 
in the natural transmission of the disease, not only because of their 
series of negative results, “but also because recent experiments have 
afforded additional evidence of the direct transmissibility or con¬ 
tagiousness of poliomyelitis, and because epidemiological studies 
appear to us to indicate that the disease is more likely transmitted 
largely through passive human virus carriers.” 

Soon after this, Kling and Levaditi (1913) published their detailed 
studies on acute anterior poliomyelitis. They considered that the 
experiments of Flexner and Clark (and Howard and Clark), who fed 
house-flies on emulsion of infected spinal cord, were under conditions 
so different from what could occur in nature that one could not 
draw precise conclusions from them regarding the epidemiology of 
the disease. They cited the experiments of Josef son (1912), as 
being under more reasonable conditions. He sought to determine 
whether the inoculation of monkeys with flies caught in the wards of 
the Hospital for Contagious Diseases at Stockholm, where they had 
been in contact with cases of poliomyelitis, would produce the 
disease. The results were completely negative. 

Kling and Lavaditi made four attempts of this kind. The flies 
were collected in places where poliomyelitics had dwelt, three, four 
and twenty-four after the beginning of the disease in the family and 
one, three, and fifteen days after the patient had left the house. 
These insects were for the greater part living and had certainly been 
in contact with the infected person. In addition, flies were used 
which had been caught in the wards of the Hospital for Contagious 
Diseases at Soderkoping, when numbers of poliomyelitics were con¬ 
fined there. Finally, to make the conditions as favorable as possible, 
the emulsions prepared from these flies were injected without previous 
filtering, since filtration often causes a weakening of the virus. In 




Infantile Paralysis or Acute Anterior Poliomyelitis 245 

spite of these precautions, all their results were negative, none of the 
inoculated animals having contracted poliomyelitis. They also 
experimented with bedbugs which had fed upon infected patients at 
various stages of the disease, but the results in these cases also were 
wholly negative. 

Kling and Levaditi considered at length the possibility of trans¬ 
mission of the disease by Stomoxys. As a result of their epidemiologi¬ 
cal studies, they found that infantile paralysis continued to spread 
in epidemic form in the dead of winter, when these flies were very 
rare and torpid, or were even completely absent. Numerous cases 
developed in the northern part of Sweden late in October and 
November, long after snow had fallen. On account of the rarity 
of the Stomoxys flies during the period of their investigations they 
v r ere unable to conduct satisfactory" experiments. In one instance, 
during a severe epidemic, they found a number of the flies in a stable 
near a house inhabited by an infected family, though none w r as 
found in the house itself. These flies were used in preparing an 
emulsion which, after filtering, was injected into the peritoneal 
cavity of a monkey. The result was wholly negative. 

As for the earlier experiments, Kling and Levaditi believe if the 
flies w r ere responsible for the transmission of the disease in the cases 
reported by Rosenau and Brues, and the first experiments of Ander¬ 
son and Frost, it w r as because the virus of infantile paralysis is elimi¬ 
nated with the nasal secretions of paralyzed monkeys and the flies, 
becoming contaminated, had merely acted as accidental carriers. 

Still further evidence against the hypothesis of the transmission 
of acute anterior poliomyelitis by Stomoxys calcitrans was brought 
forward by Sawyer and Herms (1913). Special precautions were 
used to prevent the transference of saliva or other possibly infectious 
material from the surface of one monkey to that of another, and to 
avoid the possibility of complicating the experiments by intro¬ 
ducing other pathogenic organisms from wild flies, only laboratory- 
bred flies were used. In a series of seven carefully performed experi¬ 
ments, in which the conditions were varied, Sawryer and Herms were 
unable to transmit poliomyelitis from monkey to monkey through 
the agency of Stomoxys, or to obtain any indication that the fly is the 
usual agent for spreading the disease in nature. 

The evidence at hand to date indicates that acute anterior polio¬ 
myelitis, or infantile paralysis, is transmitted by contact with in¬ 
fected persons. Under certain conditions insects may be agents in 
spreading the disease, but their role is a subordinate one. 


246 Arthropod Transmission of Disease 

Pellagra 

Pellagra is an endemic and epidemic disease characterized by a 
peculiar eruption or erythema of the skin (figs 144 and 145), digestive 

disturbances and nervous trouble. 
Insanity is a common result, rather 
than a precursor of the disease. 
The manifestations of pellagra are 
periodic and its duration indeter¬ 
minate. 

The disease is one the very name 
of which was almost unknown in the 
United States until within the past 
decade. It has usually been regarded 
as tropical, though it occurs commonly 
in Italy and in various parts of Europe. 
Now it is known that it not only 
occurs quite generally in the United 
vStates but that it is spreading. Lav- 
inder (1911) says that “There are 
certainly many thousand cases of the 
disease in this country, and the pres¬ 
ent situation must be looked upon 
with grave concern.” 

It is not within the scope of this book to undertake a general 
discussion of pellagra. The subject is of such importance to every 
medical man that we cannot do better than refer to Lavinder’s 
valuable precis. We can only touch briefly upon the entomological 
phases of the problems presented. 

The most commonly accepted theories regarding the etiology 
of the disease have attributed it to the use of Indian com as an article 
of diet. This supposed relationship was explained either on the 
basis of, (a) insufficiency of nutriment and inappropriateness of 
com as a prime article of food; (b) toxicity of com or, (c) parasitism 
of certain organisms — fungi or bacteria — ingested with either sound 
or deteriorated com. 

In 1905, Sambon proposed the theory of the protozoal origin of 
pellagra and in 1910 he marshalled an imposing array of objections 
to the theory that there existed any relationship between com and 
the disease. He presented clear evidence that pellagra existed in 
Europe before the introduction of Indian corn from America, as an 








Pellagra 


247 


article of diet, and that its spread was not pari passu with that of the 
use of com. Cases were found in which the patients had apparently 
never used com, though that is obviously difficult to establish. He 
showed that preventive measures based on the theory had been a 
failure. Finally, he believed that the recurrence of symptoms of 
the disease for successive springs, inpatients who abstained absolutely 
from the use of corn, militated against the theory. 

On the other hand, Sambon believed that the periodicity of the 
symptoms, peculiarities of distribution and seasonal incidence, and 
analogies of the symptoms to those of other parasitic diseases indi- 



145. Pellagrous eruption on the hand. After Watson. 


cated that pellagra was of protozoal origin, and that it was insect- 
borne. 

The insect carriers, he believed to be one or more species of 
Simuliidse, or black-flies. In support of this he stated that Simulium 
appears to effect the same topographical conditions as pellagra, 
that in its imago stage it seems to present the same seasonal incidence, 
that it has a wide geographical distribution which seems to cover 
that of pellagra, and that species of the genus are known to cause 
severe epizootics. Concluding from his studies in Italy, that pel¬ 
lagra was limited almost wholly to agricultural laborers, he pointed 
out that the Simulium flies are found only in rural districts, and as a 
rule do not enter towns, villages, or houses. 

When Sambon’s detailed report was published in 1910, his theory 
was seized upon everywhere by workers who were anxious to test it 




248 


Arthropod Transmission of Disease 



146. A favorite breeding place of Simulium. Ithaca, N. Y 








Pellagra 


249 


and who, in most cases, were favorably disposed towards it because 
of the wonderful progress which had been made in the understanding 
of other insect-borne diseases. In this country, the entomological 
aspects of the subject have been dealt with especially by Forbes 
(1912), and by King and Jennings, under the direction of W. D. 
Hunter, of the Bureau of Entomology, and in co-operation with 
the Thompson-McFadden Pellagra Commission of the Department 
of Tropical Medicine of the New York Post-Graduate Medical 
School. An important series of experiments with monkeys has 
been undertaken by S. J. Hunter, of Kansas, but unfortunately we have 
as yet no satisfactory evidence that these animals are susceptible 
to the disease—a fact which renders the whole problem difficult. 

The accumulated evidence is increasingly opposed to Sambon’s 
hypothesis of the transmission of pellagra by Simulium. This has 
been so clearly manifested in the work of the Thompson-McFadden 
Commission that we quote here from the report by Jennings (1914): 

“Our studies in 1912 convinced us that there was little evidence 
to support the incrimination of any species of Simulium in South 
Carolina in the transmission of pellagra. Reviewing the group as a 
whole, we find that its species are essentially “wild” and lack those 
habits of intimate association with man which would be expected 
in the vector of such a disease as pellagra. Although these flies are 
excessively abundant in some parts of their range and are moderately 
so in Spartanburg County, man is merely an incidental host, and no 
disposition whatever to seek him out or to invade his domicile seems 
to be manifested. Critically considered, it is nearer the fact that 
usually man is attacked only when he invades their habitat.” 

“As our knowledge of pellagra accumulates, it is more and more 
evident that its origin is in some way closely associated with the 
domicile. The possibility that an insect whose association with man 
and his immediate environment is, at the best, casual and desultory, 
can be active in the causation of the disease becomes increasingly 
remote.” 

“Our knowledge of the biting habits of Simulium is not complete, 
but it is evident, as regards American species at least, that these are 
sometimes not constant for the same species in different localities. 
Certain species will bite man freely when opportunity offers, while 
others have never been known to attack him. To assume that the 
proximity of a Simulium -breeding stream necessarily implies that 
persons in its vicinity must be attacked and bitten is highly fal- 


250 Arthropod Transmission of Disease 

laeious. In Spartanburg County attacks by Simulium seems to be 
confined to the immediate vicinity of the breeding-places. Our 
records and observations, exceedingly few in number, refer almost 
exclusively to such locations. Statements regarding such attacks, 
secured with much care and discrimination from a large number of 
persons, including many pellagrins, indicate conclusively that these 
insects are seldom a pest of man in this county. A certain number 
of the persons questioned were familiar with the gnats in other 
localities, but the majority were seemingly ignorant of the existence 
of such flies with biting habits. This is especially striking, in view 
of the fact that the average distance of streams from the homes of 
the pellagra cases studied was about 200 yards, many being at a 
distance of less than 100 yards, and that 78 per cent of these streams 
were found to be infested by larval Simulium. Such ignorance in a 
large number of persons cannot be overlooked and indicates strongly 
that our belief in the negligible character of local attacks by Simulium 
is well founded.” 

‘‘In localities infested by ‘sand-flies,’ mosquitoes, etc., these 
pests are always well known and the ignorance described above is 
very significant.” 

‘‘Such positive reports as we received nearly always referred to 
bites received in the open, along streams, etc., and observations made 
of their attack were of those on field laborers in similar situations. 
Males engaged in agricultural pursuits are almost exempt from 
pellagra in Spartanburg County. During the season of 1913, in 
some two or three instances, observations were made of the biting 
of Simulium and some additional and entirely creditable reports 
were received. These observations and reports were under condi¬ 
tions identical with those referred to in the reports of 1912 and con¬ 
firm the conclusions based on the observations of that year. I 
would repeat with emphasis that it is inconceivable that a fly of the 
appearance and habits of the prevalent species of Simulium could be 
present in such a region, especially about the haunts of man and 
attack him with sufficient frequency and regularity to satisfactorily 
account for so active and prevalent a disease as pellagra without 
being a well-known and recognized pest.” 

‘‘In connection with the conditions in the Piedmont region of 
South Carolina, it may be well to cite the results of a study of those 
in the arid region of western Texas.” 


Pellagra 


251 


“In May, 1913, in company with Capt. J. F. Siler of the Thomp- 
son-McFadden Pellagra Commission, I visited the region of which 
Midland in Midland County is the center. This region is very dry 
and totally devoid of running water for a long distance in every 
direction. The only natural source of water-supply, a few water 
holes and ponds, were visited and found to be of such a nature that 
the survival of Simulium, far less its propagation in them, is abso¬ 
lutely impossible. The nearest stream affording possibilities as a 
source of Simulium is 60 miles away, while the average distance of 
such possibility is not less than 100 miles.” 

“Artificial sources of water-supply were also investigated care¬ 
fully and were found to offer no opportunity for the breeding of 
Simulium." 

“At Midland the histories of five cases of pellagra were obtained, 
which gave clear evidence that this place or its immediate vicinity 
was the point of origin. Persons of long residence in the country 
were questioned as to the occurrence of such flies as Simulium and 
returned negative answers. These included a retired cattle owner, 
who is a man of education and a keen observer, an expert veterinarian 
stationed in the country who has the cattle of the country under 
constant observation, and a practical cattle man, manager of a ranch 
and of wide experience. The latter had had experience with ‘Buf¬ 
falo gnats’ in other localities (in the East) and is well acquainted 
with them. His close personal supervision of the cattle under his 
charge, makes it practically certain that he would have discovered 
these gnats had they been present in the country.” 

“At the time the study was made, Simulium was breeding and 
active in the adult state in the vicinity of Dallas, Texas, in the 
eastern part of the state. We have here a region in which cases of 
pellagra have originated, yet in which Simulium does not and cannot 
breed.” 

Other possible insect vectors of pellagra have been studied in 
great detail and the available evidence indicates that if any insect 
plays a role in the spread of the disease, Stomoxys calcitrans most 
nearly fills the conditions. This conclusion was announced by 
Jennings and King in 1912, and has been supported by their subse¬ 
quent work. 

Yet, after all the studies of the past decade, the old belief that 
pellagra is essentially of dietary origin is gaining ground. Gold- 
berger, Waring and Willets (1914) of the United States Public Health 


252 Arthropod Transmission of Disease 

Sendee summarize their conclusions in the statement, (i) that it is 
dependent on some yet undetermined fault in a diet in which the 
animal or leguminous protein component is disproportionately large 
and (2) that no pellagra develops in those who consume a mixed, 
well-balanced, and varied diet, such, for example, as that furnished 
by the Government to the enlisted men of the Army, Navy, and 
Marine Corps. 

Leprosy 

Leprosy is a specific, infectious disease due to Bacillus lepree, and 
characterized by the formation of tubercular nodules, ulcerations, 
and disturbances of sensation. In spite of the long time that the 
disease has been known and the dread with which it is regarded, 
little is known concerning the method of transfer of the causative 
organism or the means by which it gains access to the human body. 

It is known that the bacilli are to be found in the tubercles, the 
scurf of the skin, nasal secretions, the sputum and, in fact in prac¬ 
tically all the discharges of the leper. Under such conditions it is 
quite conceivable that they may be transferred in some instances 
from diseased to healthy individuals through the agency of insects 
and other arthropods. Many attempts have been made to demon¬ 
strate this method of spread of the disease, but with little success. 

Of the suggested insect carriers none seem to meet the conditions 
better than mosquitoes, and there are many suggestions in literature 
that these insects play an important role in the transmission of 
leprosy. The literature has been reviewed and important experi¬ 
mental evidence presented by Currie (1910). He found that mosqui¬ 
toes feeding, under natural conditions, upon cases of nodular leprosy 
so rarely, if ever, imbibe the lepra bacillus that they cannot be 
regarded as one of the ordinary means of transference of this bacillus 
from lepers to the skin of healthy persons. He believes that the 
reason that mosquitoes that have fed on lepers do not contain the 
lepra bacillus is that when these insects feed they insert their probos¬ 
cis directly into a blood vessel and thus obtain bacilli-free blood, 
unmixed with lymph. 

The same worker undertook to determine whether flies are able 
to transmit leprosy. He experimented with five species found in 
Honolulu, — Musca domestica, Sarcophaga pallinervis, Sarcophaga 
barbata, Volucella obesa and an undetermined species of Lucilia. 
The experiments with Musca domestica were the most detailed. 


Leprosy 


253 


From these experiments he concluded, first, that all of the above- 
named flies, when given an opportunity to feed upon leprous fluids, 
will contain the bacilli in their intestinal tracts and feces for several 
days after such feeding. Second, that considering the habits of 
these flies, and especially those of Musca domestica, it is certain that, 
given an exposed leprous ulcer, these insects will frequently convey 
immense numbers of lepra bacilli, directly or indirectly, to the skins, 
nasal mucosa, and digestive tracts of healthy persons. Additional 
evidence along this line has recently been brought forward by 
Honeij and Parker (1914), who incriminate both Musca domestica 
and Stomoxys calcitrans. Whether or not such insect-borne bacilli 
are capable of infecting persons whose skin and mucosa are thus 
contaminated, Currie was unwilling to maintain, but he concludes 
that until we have more accurate knowledge on this point, we are 
justified in regarding these insects with grave suspicion of being 
one of the means of disseminating leprous infection. 

Various students of the subject have suggested that bed-bugs 
may be the carriers of leprosy and have determined the presence of 
acid-fast bacilli in the intestines of bed-bugs which had fed on leprous 
patients. Opposed to this, the careful experiments of Thompson 
(1913) and of Skelton and Parkham (1913) have been wholly nega¬ 
tive. 

Borrel has recently suggested that Demodex, may play a role in 
spreading the infection in families. Many other insects and acariens 
have been suggested as possible vectors, but the experimental data 
are few and in no wise conclusive. The most that can be said is that 
it is quite possible that under favorable conditions the infection 
might be spread by any of the several blood-sucking forms or by 
house-flies. 


Verruga peruviana 

Verruga peruviana is defined by Castellani and Chalmers as “a 
chronic, endemic, specific, general disorder of unknown origin, not 
contagious, but apparently inoculable, and characterized by an ir¬ 
regular fever associated with rheumatoid pains, anemia, followed 
by granulomatous swellings in the skin, mucous membranes, and 
organs of the body.” It has been generally believed by medical 
men interested that the comparatively benign eruptive verruga is 
identical with the so-called Oroya, or Carrion’s fever, a malignant 
type. This view is not supported by the work of Strong, Tyzzer 
and Brues, (1913). 


254 


Arthropod Transmission of Disease 


The disease is confined to South America and to definitely limited 
areas of those countries in which it does occur. It is especially 
prevalent in some parts of Peru. 

The causative organism and the method of transfer of verruga 
are unknown. Castellani and Chalmers pointed out in 1910 that the 
study of the distribution of the disease in Pem would impress one 
with the similarity to the distribution of the Rocky Mountain fever 
and would lead to the conclusion that the astiological cause must in 
some way be associated with some blood-sucking animal, perhaps an 
arachnid, and that this is supported by the fact that the persons 
most prone to the infection are those who work in the fields. 

More recently, Townsend (1913), in a series of papers, has main¬ 
tained that verruga and Carrion’s disease are identical, and that they 
are transmitted to man by the bites of the Psychodid fly, Phlebotomus 
verrucarum. He succeeded in producing the eruptive type of the 
disease in experimental animals by injecting a physiological salt 
trituration of wild Phlebotomus flies. A cebus monkey was exposed 
from October 10 to November 6, by chaining him to a tree in the 
verruga zone, next to a stone wall from which the flies emerged in 
large numbers every night. Miliar eruption began to appear on the 
orbits November 13 and by November 21, there were a number of 
typical eruptions, with exudation on various parts of the body 
exactly like miliar eruptive sores commonly seen on legs of human 
cases. 

An assistant in the verruga work, George E. Nicholson, contracted 
the eruptive type of the disease, apparently as a result of being bitten 
by the Phlebotomus flies. He had slept in a verruga zone, under a 
tight net. During the night he evidently put his hands in contact 
with the net, for in the morning there were fifty-five unmistakable 
Phlebotomus bites on the backs of his hands and wrists. 

Townsend believes that in nature, lizards constitute the reservoir 
of the disease and that it is from them that the Phlebotomus flies 
receive the infection. 


Cancer 

There are not wanting suggestions that this dread disease is 
carried, or even caused, by arthropods. Borrel (1909) stated that 
he had found mites of the genus Demodex in carcinoma of the face 
and of the mammas. He believed that they acted as carriers of the 
virus. 



Cancer 


255 


Saul (1910) and Dahl (1910) go much further, since they attribute 
the production of the malignant growth to the presence of mites 
which Saul had found in cancers. These Dahl described as belonging 
to a new species, which he designated Tarsonemus hominis. These 
findings have since been confirmed by several workers. Neverthe¬ 
less, the presence of the mite is so rare that it cannot be regarded as 
an important factor in the causation of the disease. The theory 
that cancer is caused by an external parasite is given little credence 
by investigators in this field. 

In conclusion, it should be noted that the medical and entomolog¬ 
ical literature of the past few years abounds in suggestions, and in 
unsupported direct statements that various other diseases are insect- 
borne. Knab (1912) has well said “Since the discovery that certain 
blood-sucking insects are the secondary hosts of pathogenic para¬ 
sites, nearly every insect that sucks blood, whether habitually or 
occasionally, has been suspected or considered a possible transmitter 
of disease. No thought seems to have been given to the conditions 
and the characteristics of the individual species of blood-sucking 
insects, which make disease transmission possible.” 

He points out that “in order to be a potential transmitter of human 
blood-parasites, an insect must be closely associated with man and 
normally have opportunity to suck his blood repeatedly. It is not 
sufficient that occasional specimens bite man, as, for example, is the 
case with forest mosquitoes. Although a person may be bitten by a 
large number of such mosquitoes, the chances that any of these 
mosquitoes survive to develop the parasites in question, (assuming 
such development to be possible), and then find opportunity to bite 
and infect another person, are altogether too remote. Applying 
this criterion, not only the majority of mosquitoes but many other 
blood-sucking insects, such as Tabanidae and Simuliidse, may be 
confidently eliminated. Moreover, these insects are mostly in 
evidence only during a brief season, so that we have an additional 
difficulty of a very long interval during which there could be no prop¬ 
agation of the disease in question.” He makes an exception of 
tick-borne diseases, where the parasites are directly transmitted from 
the tick host to its offspring and where, for this reason, the insect 
remains a potential transmitter for a very long period. He also 
cites the trypanosome diseases as possible exceptions, since the causa¬ 
tive organisms apparently thrive in a number of different vertebrate 
hosts and may be transmitted from cattle, or wild animals, to man. 


256 


Arthropods Transmission of Disease 


Knab’s article should serve a valuable end in checking irrespon¬ 
sible theorizing on the subject of insect transmission of disease. 
Nevertheless, the principles which he laid down cannot be applied 
to the cases of accidental carriage of bacterial diseases, or to those 
of direct inoculation of pyogenic organisms, or of blood parasites 
such as the bacillus of anthrax, or of bubonic plague. Accumulated 
evidence has justified the conclusion that certain trypanosomes 
pathogenic to man are harbored by wild mammals, and so form an 
exception. Townsend believes that lizards constitute the natural 
reservoir of verruga; and it seems probable that field mice harbor 
the organism of tsutsugamushi disease. Such instances are likely to 
accumulate as our knowledge of the relation of arthropods to disease 
broadens. 


'CHAPTER XII 


HOMINOXIOUS ARTHROPODS 

The following synoptic tables are presented in the hope that they 
may be of service in giving the reader a perspective of the relation¬ 
ships of the Arthropoda in general and enabling him to identify the 
more important species which have been found noxious to man. 
Though applicable chiefly to the arthropods found in the United 
States, exotic genera and species which are concerned in the trans¬ 
mission of disease are also included. For this reason the keys to the 
genera of the Muscids of the world are given. As will be seen, the 
tables embrace a number of groups of species which are not injurious. 
This was found necessary in order that the student might not be 
lead to an erroneous determination which would result were he to 
attempt to identify a species which heretofore had not been considered 
noxious, by means of a key containing only the noxious forms. The 
names printed in bold faced type indicate the hominoxious arthropods 
which have been most commonly mentioned in literature. 

CRUSTACEA 

Arthropods having two pairs of antennae which are sometimes 
modified for grasping, and usually with more than five pairs of legs. 
With but few exceptions they are aquatic creatures. Representatives 
are: Crabs, lobsters, shrimps, crayfish, water-fleas, and woodlice. 
To this class belongs the Cyclops (fig. 122) a genus of minute aquatic 
crustaceans of which at least one species harbors Dracunculus medi- 
nensis, the Guinea worm (fig. 121). 

MYRIAPODA 

Elongate, usually vermiform, wingless, terrestrial creatures having 
one pair of antennas, legs attached to each of the many intermediate 
body segments. This group is divided into two sections, now usually 
given class rank: the Diplopoda or millipeds (fig. 13), commonly 
known as thousand legs, characterized by having two pairs of legs 
attached to each intermediate body segment, and the Chilopoda 
or centipeds (fig. 14) having only one pair of legs to each body seg¬ 
ment. 


257 


258 


Hominoxious Arthropods 


ARACHN1DA 

In this class the antennae are apparently wanting, wings are never 
present, and the adults are usually provided with four pairs of legs. 
Scorpions, harvest-men, spiders, mites, etc. 

HEXAPODA (Insects) 

True insects have a single pair of antennae, which is rarely vestigial, 
and usually one or two pairs of wings in the adult stage. Familiar 
examples are cockroaches, crickets, grasshoppers, bugs, dragonflies, 
butterflies, moths, mosquitoes, flies, beetles, ants, bees and wasps. 

ORDERS OF THE ARACHNIDA 

a. Abdomen distinctly segmented. A group of orders including scorpions, 
(fig. 11), whip-scorpions (fig. 10), pseudo-scorpions, solpugids (fig. 12) 

harvest-men (daddy-long-legs or harvestmen), etc. Arthrogastra 

aa. Abdomen unsegmented, though sometimes with numerous annulations 

.SPHiEROGASTRA 

b. A constriction between cephalothorax and abdomen (fig. 7). True Spiders 

.Araneida 

bb. No deep constriction between these parts. 

c. Legs usually well developed, body more or less depressed (fig. 49). Mites 

. Acarina 

cc. Legs stumpy or absent, body more or less elongate or vermiform, or if 
shorter, the species is aquatic or semi-aquatic in habit, 

d. Four pairs of short legs; species inhabiting moss or water. Water- 

bears . Tardigrada 

dd. Two pairs of clasping organs near the mouth, instead of legs, in the 
adult; worm-like creatures parasitic within the nasal passages, 
lungs, etc. of mammals and reptiles (fig. 148). Tongue worms. 
.Linguatulina 













Acarina 


259 


ACARINA* 

a. Abdomen annulate, elongate; very minute forms, often with but four legs 

(fig. 62).Demodicoidea 

b. With but four legs of five segments each. Living on plants, often forming 

galls . Eriophyid^e 

bb. With eight legs, of three segments each. Living in the skin of mammals 

. Demodicid,® 

To this family belongs the genus Demodex found in the sebaceous glands 
and hair follicles of various mammals, including man. D. phylloides 
Csokor has been found in Canada on swine, causing white tubercles 
on the skin. D. bovis Stiles has been reported from the United States 
on cattle, upon the skin of which they form swellings. D. folliculorum 
Simon is the species found on man. See page 78. 
aa. Abdomen not annulate nor prolonged behind; eight legs in the adult stage, 
b. With a distinct spiracle upon a stigmal plate on each side of the body (usu¬ 
ally ventral) above the third or fourth coxae or a little behind (fig. 50); 
palpi free; skin often coriaceous or leathery; tarsi often with a sucker, 

c. Hypostome large (fig. 50), furnished below with many recurved teeth; 
venter with furrow's, skin leathery; large forms, usually parasitic 

. IXODOIDEA 

d. Without scutum but covered by a more or less uniform leathery integu¬ 
ment; festoons absent; coxae unarmed, tarsi without ventral spurs; 
pulvilli absent or vestigial in the adults; palpi cylindrical; sexual 

dimorphism slight. Argasid^e 

e. Body flattened, oval or rounded, with a distinct flattened margin 
differing in structure from the general integument; this margin 
gives the body a sharp edge which is not entirely obliterated even 
w'hen the tick is full fed. Capitulum (in adults and nymphs) 
entirely invisible dorsally, distant in the adult by about its own 

length from the anterior border. Eyes absent.Argus Latr. 

f. Body oblong; margin with quadrangular cells; anterior tibiae and 
metatarsi each about three times as long as broad. On poultry, 

southwest United States.A. persicus miniatus 

A. brevipes Banks, a species with proportionately shorter legs has 
been recorded from Arizona. 

ff. With another combination of characters. About six other species 
of Argas from various parts of the world, parasitic on birds and 
mammals. 

ee. Body flattened when unfed, but usually becoming very convex on 
distention; anterior end more or less pointed and hoodlike; 
margin thick and not clearly defined, similar in structure to the 
rest of the integument and generally disappearing on distention; 
capitulum subterminal, its anterior portions often visible dorsally 
in the adult; eyes present in some species, 
f. Integument pitted, without rounded tubercles; body provided 
wfith many short stiff bristles; eyes absent. On horses, cattle 

and man (fig. 48) . Otiobius Banks. 

O.megnini, a widely distributed species, is the type of this genus. 
♦Adapted from Banks, Nuttall, Warburton, Stiles, et . al . 











260 


Hominoxious A rth ropods 


ff. Integument with rounded tubercles or granules; body without stiff 

bristles.Omithodoros Koch. 

g. Two pairs of eyes; tarsi IV with a prominent sub terminal spur 
above; leg I strongly roughened. On cattle and man. 


.O. coriaceus 

gg. No eyes; no such spur on the hind tarsi. 

h. Tarsi I without humps above. O. talaje. 

lih. Tarsi I with humps above. 

i. Tarsi IV without distinct humps above. On hogs, cattle 

and man.O. turicata 


ii. Tarsi IV with humps nearly equidistant (fig. 142). Africa. 

. O. moubata 



dd. With scutum or shield (fig. 50); festoons usually present; coxa? 
usually armed with spurs, tarsi generally with one or two ventral 
spurs; pulvilli present in the adults; sexual dimorphism pronounced 

. IXODIDiE 

e. With anal grooves surrounding anus in front; inornate; without eyes; 
no posterior marginal festoons; venter of the male with non¬ 
salient plates. Numerous species, 14 from the United States, 
among them I. ricinus (fig. 49 and 50), scapularis, cookei, hexa- 
gonus, bicornis. Ixodes Latr. (including Ceratixodes). 

ee. With anal groove contouring anus behind, or groove faint or obsolete, 

f. With short palpi (fig. 149). 

g. Without eyes, inornate, with posterior marginal festoons; male 
without ventral plates. Numerous species. II. chordeilis 

and leporis-palustris from the United States . 

. Hmmaphysalis Koch. 














Acarina 


261 



loO. Stigmal plate of Dermacentor andersoni; (a) of male, (6) of female. After Stiles. 

(c) Dermacentor variabilis, male - ( d ) Glyciphagus obesus; ( e ) Otodectes 
cynotis; (/) Tyroglyphus lintneri; (g) Tarsonemus pallidus; (h) anal plate 
and mand’ble of Liponyssus; (c) to ( h ) after Banks. 


















262 


Hominoxious A rthropods 


gg. With eyes. 

h. Anal groove distinct; posterior marginal festoons present, 

i. Base of the capitulum (fig. 150c) rectangular dorsally; 

usually ornate.Dermacentor Koch. 

j. Adults with four longitudinal rows of large denticles on 
each half of hypostome; stigmal plate nearly circular, 
without dorso-lateral prolongation, goblets very large, 
attaining 43/* to 115/^ in diameter; not over 40 per 
plate, each plate surrounded by an elevated row of 
regularly arranged supporting cells; white rust want¬ 
ing; base of capitulum distinctly broader than long, 
its postero-lateral angles prolonged slightly, if at all; 
coxae I with short spurs; trochanter I with small 
dorso-terminal blade. Texas, Arizona, etc. D. nitens 



151. Rhipicephalus bursa, male. 
After Nuttall and Warburton. 


jj. Adults with three longitudinal rows of large denticles on 
each half of hypostome; goblet cells always more 
than 40 per plate; whitish rust usually present, 

k. Dorso-lateral prolongation of stigmal plate small or 
absent; plates of the adults distinctly longer than 
broad; goblet cells large, usually 30/u to 85M in 
diameter, appearing as very coarse punctations on 
untreated specimens, but on specimens treated 
with caustic potash they appear very distinct in 
outline; base of capitulum distinctly (usually about 
twice) broader than long, the postero-lateral angles 
distinctly produced caudad; spurs of coxae I long, 
lateral spur slightly longer than median; tro¬ 
chanter I with dorso-terminal spur. D. albipictus, 
(= variegatus), salmoni, nigrolineatus. 








Acarina 


263 


kk. Dorsolateral prolongation of stigmal plate distinct. 

I . Body of plate distinctly longer than broad; goblet 

cells of medium size, usually 17.5M to 35/x or 40M in 
diameter, appearing as medium sized punctua¬ 
tions on untreated specimens, but on the speci¬ 
mens treated with caustic potash they appear 
very distinct in outline, which is not circular; 
base of capitulum usually less than twice as broad 
as long, the postero-lateral angles always dis¬ 
tinctly prolonged caudad. 

m. Trochanter I with distinct dorso-subterminal 
retrograde sharp, digitate spur; postero¬ 
lateral angles of capitulum pronouncedly 
prolonged caudal, 112/x to 160 m long; goblet 
cells attain 13M to 40 m in diameter; type 

locality California.D. occidentalis 

mm. Trochanter I with dorso-terminal blade; postero¬ 
lateral angles of capitulum with rather short 
prolongations. 

n. Stigmal plate small, goblet cells not exceeding 
45 in the male or 100 in the female; scutum 
with little rust, coxa I with short spurs, the 
inner distinctly shorter than the outer 

. D. parumapertus-marginatus 

nn. Stigmal plate larger; goblet cells over 70 in 
the male and over 100 in the female; coxa I 
with longer spurs, inner slightly shorter 
than the outer; scutum with considerable 
rust.D. venustus* 

II . Goblet cells small, rarely exceeding 17.6 m, occasional¬ 

ly reaching 19M in diameter; on untreated speci¬ 
mens they appear as very fine granulations, and on 
specimens treated with caustic potash they may 
be difficult to see, but their large number can 
be determined from the prominent stems of the 
goblets; surface of outline of the goblets dis¬ 
tinctly circular; base of the capitulum usually less 
than twice as broad as long, the postero-lateral 
angle distinctly prolonged caudad; spurs of 

coxae I long. 

. D. reticulatus and electus (= variabilis?) 

ii. Base of the capitulum (fig. 151) usually hexagonal (except 
in the male of puchellus ); and usually inornate. 

*Dr. C. W. Stiles considers the species which is responsible for spotted fever distinct from the 
venustus of Banks, separating it as follows: 

Goblet cells about 75 in the male or 105 in the female. Texas. D. venustus. 

Goblet cells 157 in the male, or 120 in the female; stigmal plate shaped as shown in the figure 
(figs. 150 a, b). Montana, etc. D. andersoni. 








264 


Hominoxious Arthropods 


j. No ventral plate or shield in either sex (fig. 153). R. 

bicomis from the United States ... Rhipicentor Nuttall 
jj. Males with a pair of adanal shields, and usually a pair of 
accessory adanal shields. Numerous species, among 
them R. sanguineus (fig. 154) and texanus, the latter 

from the United States. Rhipicephalus Koch 

hh. Anal grooves faint or obsolete; no marginal festoons. 

i. Short palpi; highly chitinized; unfed adults of large size; 
coxae conical; male with a median plate prolonged in two 
long spines projecting caudad; segments of leg pair IV 

greatly swollen (fig. 155, 156). M. winlhemi . 

. Margaropus Karsch 




152 . Monieziella (Histiogaster) emtomophaga-spermatica, ventral aspect, 
male and female. After Trouessart, 

ii. Very short palpi, ridged dorsally and laterally; slightly 
chitinized; unfed adults of smaller size; coxae I bifid; 
male with adanal and accessory adanal shields (fig. 139). 

B. annulatus.Boophilus Curtis 

ff. Palpi longer than broad (fig. 157). 

g. Male with pair of adanal shields, and two posterior abdominal 
protrusions capped by chitinized points; festoons present or 
absent. Several species, among them H. aegypticum (fig. 140) 

from the old world.Hyalomma Koch 

gg. Male without adanal shields but small ventral plaques are 
occassionally present close to the festoons. Many species, a 
few from the Unted States (fig. 157). . . . Amblyomma Koch 
h. Coxa I with but one spine; metatarsi (except 1 ) with two 

thickened spurs at tips . A. maculatum 

hh. Coxa I with two spines; metatarsi without stout spurs at 
tips, only slender hairs. 












Acarina 


265 


i. Projections of coxa I blunt and short. Large species on the 

gopher tortoise in Florida. A. tuberculatum 

ii. Projections of coxa I longer, and at least one of them sharp 

pointed; second segment of palpus twice as long as the 
third; coxa IV of the male with a long spine, 
j. Porose areas nearly circular; shield of both sexes pale 
yellowish, with some silvery streaks and marks, and 
some reddish spots; shield of female as broad as long. 

.A. cajennense ( = mixtum). 

jj. Porose areas elongate, shield brown, in the female with 
an apical silvery mark, in the male with two small 
and two or four other silvery spots; shield of the fe¬ 
male longer than broad (fig 158 e). .A. americanum. 



internal spur 
Exttrn&l spu^n 


Kcc 31 
Ccxjx- ?rr 
CmcxK 2 Y. 

•Spi cac /e— 


153 . Rhipicentor bicornis, ventral aspect, male. After Nuttall and 
Warburton. 


rrcPcoC 




:. Hypostome small, without teeth, venter without furrows; body often 
with coriaceous shields, posterior margin of the body never crenulate 

(i.e. without festoons); no eyes.GAMASOIDEA. 

d. Parasitic on vertebrates; mandibles fitted for piercing; body sometimes 

constricted . Dermanyssid^e. 

e. Anal plate present. DERMANYSSiNbE. 

f. Body short; legs stout, hind pair reaching much beyond the tip of 

the body. On bats. Pteroptus Dufour. 

ff. Body long; hind legs not reaching beyond the tip of the body, 

g. Peritreme on the dorsum, very short; body distinctly con¬ 
stricted . Ptilonyssus Berl. 

gg. Peritreme on the venter, longer; body not distinctly con¬ 
stricted. 

h. Mandibles in both sexes chelate. Parasitic on bats, mice 

and birds (fig. 150, h).Liponyssus Kol. 

The species L. (= Leiognathus) sylviarum frequents the 
nests of warblers. An instance is on record of these mites 
attacking man, causing a pruritis. 




















266 


Hominoxious Arthropods 


hh. Mandibles in the male chelate (fig. 158 j), in the female long, 

styliform. Parasitic on birds.Dermanyssus Dug. 

Two species of importance may be noted, D. hirundinus 
and D. gallinae. The latter (fig. 51) is a serious pest 
of poultry, sometimes attacking man, causing itching 
and soreness. 

ee. Anal plate absent. In lungs and air passages of some mammals. 

. Halarachnin^;. 

dd. Free or attached to insects, rarely on vertebrates. 

e. First pair of legs inserted within the same body opening as the oral 
tube; genital apertures surrounded by the sternum. On in¬ 
sects . Uropodid^e. 



154 . Rhieephalus sanguineus, male. 

After Nuttall and Warbur- 
ton. 


ee. First pair of legs inserted at one side of the mouth opening; male 
genital aperture usually on the anterior margin of the sternal 

plate .Gamasidae. 

This family contains a number of genera, some of which are found 
upon mammals, though the majority affect only other artho- 
pods. One species, Laelaps stabularis, frequents the bedding 
in stables, and in one instance at least, has occasioned irri¬ 
tation and itching, in man. 

bb. No distinct spiracle in the stigmal plate on each side of the body. 

c. Body usually coriaceous, with few hairs, with a specialized seta arising 
from a pore near each posterior corner of the cephalothorax; no eyes; 
mouth parts and palpi very small; ventral openings of the abdomen 


large; tarsi without sucker. Not parasitic.ORIBATOIDEA. 

cc. Body softer; without such specialized seta. 

d. Aquatic species.HYDRACHNOIDEA 

dd. Not aquatic. 












A carina 


267 


. Palpi small, three segmented, adhering for some distance to the lip; 
ventral suckers at genital opening or near anal opening usually 
present; no eyes; tarsi often end in suckers; beneath the skin on 
the venter are seen rod-like epimera that support the legs; body 
often entire. Adults frequently parasitic. .. .SARCOPTOIDEA. 

f. With tracheae; no ventral suckers; legs ending in claws; body 
divided into cephalothorax and abdomen; the female with a 
clavate hair between legs I and II. Usually not parasitic 

on birds and mammals. Tarsonemid.® 

g. Hind legs of female ending in claw and sucker as in the other 

pairs. Pediculoidin je 

To this sub-family belongs the genus PEDICUXOIDES 
P. ventricosus is described on page 69. 



155. Margaropus winthemi, male. After 156. Margaropus winthemi, 
Nuttall and Warburton. capitulum and scutum, 

After Nuttall and War- 
burton. 

gg. Hind legs of the female end in long hairs. TarSONEMINjE 

Tarsonemus intectus Karpelles, normally found upon grain, 
is said to attack man in Hungary and Russia. Other 
species of the genus affect various plants (c.f. fig. 150, g). 
ff. Without tracheae; no such clavate hair. 

g. Genital suckers usually present; integument usually without 
fine parallel lines. 

h. Legs short, without clavate hair on tarsi I and II. On 

insects. Canestrinid^e. 

hh. Legs longer, with a clavate hair on tarsi I and II, Not 

normally parasitic except on bees. Tyroglyphid^e 

i Dorsal integument more or less granulate; claws very weak, 
almost invisible; some hairs of the body plainly feathered; 

ventral apertures large.Glyciphagus Her. 

This genus occurs in the United States. In Europe the 
mites have been found feeding on all sorts of substances. 
They are known as sugar mites and cause the disease 














268 


Hominoxious A rth ropods 


known as grocer’s itch. G. domesticus and G. pru- 
norum are old world species (fig. 150, d). 
ii. Dorsal integument not granulate; claws distinct; no 
prominent feathered hairs; ventral aperture small, 

j. Mandibles not chelate; elongate, and toothed below; 
body without long hairs; palpi enlarged at tip and 
provided with two divergent bristles. Species feed on 

decaying substances. Histiostoma Kram. 

jj. Mandibles chelate; palpi not enlarged at the tip, nor 
with two bristles. 

k. No clavate hair on the base of tarsi I and II; no 
suture between cephalothorax and abdomen. Live 

on bees or in their nests. Trichotarsus Can. 

kk. A clavate or thickened hair at the base of tarsi I and II. 

I . The bristle on the penultimate segment of the legs 

arises from near the middle; no suture between the 
cephalothorax and abdomen. The species, some 
of which occur in the United States, feed on dried 
fruit, etc. Ccirpoglyphus Robin. 

II . The bristle on the penultimate segment of the legs 

arise from near the tip; a suture between cephalo¬ 
thorax and abdomen. 

m. Cephalothorax w r ith four distinct and long bristles 
in a transverse row; tarsi I and II about twice 
as long as the preceding segment (fig. 150 f) 

.Tyroglyphus Latr. 

n. Some bristles on tarsi I and II near middle, 
distinctly spine-like; the sense hair about its 
length from the base of the segment. Several 
species in the United States belong to this 
group. 

nn. No spine-like bristles near the middle of the 
tarsi; sense hair not its length from the base 
of the segment. 

o. Of the terminal abdominal bristles, only two 
are about as long as the abdomen; 1 eg I 
of the male greatly thickened and with a 
spine at apex of the femur below. . T. farinas. 
00. Of the terminal abdominal bristles at least 
six or more are very long, nearly as long 
as the body. 

p. Bristles of the body distinctly plumose or 
pectinate; tarsi very long. . T. longior. 
pp. Bristles of the body not pectinate. 

q. In mills, stored foods, grains, etc. Third 
and fourth joints of hind legs scarcely 
twice as long as broad; abdominal 
bristles not unusually long; legs I 






Acarina 


269 


and II of the male not unusually 

stout. T. americanus. 

qq. With other characters and habits. 
T. lintneri (fig. 150 f) the mushroom 
mite, and several other species, 
mm. Cephalothorax with but two long distinct 
bristles (besides the frontal pair), but some¬ 
times a very minute intermediate pair; 
tarsi I and II unusually short and not twice 
as long as the preceding segment, 
n. Tarsi with some stout spines. Rhizoglyphus Clap. 
The species of this genus are vegetable feed¬ 
ers. Several occur in the United States. 
R. parsiticus and R. spinitarsus have been 
recorded from the old world, attacking human 
beings who handle affected plants, 
nn. Tarsi with only fine hairs. . Monieziella Berl. 
The species of this genus, as far as known, 
are predaceous or feed on recently killed 
animal matter. Several species occur 
in the United States. M. (= Histiogaster) 
entomophaga (fig. 152) from the old 
world has been recorded as injurious 
to man. 

gg. Genital suckers absent; integument with fine parallel lines. 
Parasitic on birds and mammals, 
h. Possessing a specially developed apparatus for clinging to 

hairs of mammals. Listrophorid.e. 

hh. Without such apparatus. 

i. Living on the plumage of birds . Analgesid.-e. 

ii. In the living tissues of birds and mammals. 

j. Vulva longitudinal. In the skin and cellular tissues of 

birds. Cytoleichid.e. 

This family contains two species, both occurring in the 
United States on the common fowl. Laminosioples 
cysticola occurs on the skin and also bores into the 
subcutaneous tissue where it gives rise to a cal¬ 
careous cyst. Cytoleichus nudus is most commonly 
found in the air passages and air cells, 
jj. Vulva transverse. In the skin of mammals and birds 

. SARCOPTIDjE 

k. Anal opening on the dorsum. 

I . Third pair of legs in the male without apical suckers. 

On cats and rabbits . Notoedres Rail. 

The itch mite of the cat, N. cati (fig. 61) has been 
recorded on man. 

II . Third leg in the male with suckers. On bats. . . . 

. Prosopodectes Can. 









270 


Hominoxious Arthropods 


kk. Anal opening below. 

I . Pedicel of the suckers jointed; mandibles styliform 

and serrate near the tip . Psoroptes Gerv. 

P. communis ovis is the cause of sheep scab. 

II . Pedicel of the suckers not jointed; mandibles 
chelate. 

m. No suckers on the legs of the females; parasitic 
on birds, including chickens. C. mutans is 
itch mite of chickens. Cnemidocoptes Furst. 
mm. Suckers at least on legs I and II; parasitic on 
mammals. 

n. Legs very short; in the male the hind pairs 

equal in size; body usually short . 

. Sarcoptes Latr. 

S. scabiei is the itch mite of man (fig. 56). 



157. Amblyomma, female. After Nuttall 
and Warburton. 


nn. Legs more slender; in the male the third pair 
is much larger than the fourth; body more 
elongate. 

o. Female w r ith suckers on the fourth pair of 
legs. Species do not burrow in the skin, 
but produce a scab similar to sheep scab. 
They occur in the ox, horse, sheep and goat 

.Chorioptes Gerv. 

C. symbiotes bovis of the ox has been 
recorded a few times on man. 

00. Female without suckers to the fourth legs, 

p. Hind part of the male abdomen with two 

lobes. On a few wild animals . 

. Caparinia Can. 








Acarina 


271 


pp. Hind part of the male abdomen without 
lobes. Live in ears of dogs and cats 

.. . Otodectes Canestr. 

0 . cynotis Hering (fig. 150 e) has been 
taken in the United States. 

:. Palpi usually of four or five segments, free; rarely with ventral 
suckers near genital or anal openings; eyes often present; tarsi 
never end in suckers; body usually divided into cephalothorax 
and abdomen; rod-like epimera rarely visible; adults rarely 
parasitic. 

f. Last segment of the palpi never forms a thumb to the preceding 
segment; palpi simple, or rarely formed to hold prey; body 

with but few hairs.EUPODOIDEA. 

g. Palpi often geniculate, or else fitted for grasping prey; mandi¬ 
bles large and snout like; cephalothorax with four long 
bristles above, two in front, two behind; last segment of leg I 

longer than the preceding segment, often twice as long. 

. BdELLID/E. 

gg. Palpi never geniculate (fig. 158a), nor fitted for grasping prey: 
beak small; cephalothorax with bristles in different arrange¬ 
ment; last segment of leg I shorter or but little longer than 
the preceding joint; eyes when present near posterior 

border . Eupodid^e 

Moniez has described a species from Belgium (Tydeus 

molestus) which attacks man. It is rose colored; eye¬ 
less; its legs are scarcely as long as its body, the hind 
femur is not thickened; the mandibles are small and the 
anal opening is on the venter. The female attains a 
length of about 0.3 mm. 

ff. Last segment of the palpus forms a thumb to the preceding, which 
ends in a claw (with few exceptions); body often with many 

hairs (fig. 158 k).TROMBIDOIDEA. 

g. Legs I and II with processes bearing spines; skin with several 

shields; coxae contiguous.C/ECULID.E. 

gg. Legs I and II without such processes; few if any shields, 

h. Palpi much thickened on the base, moving laterally, last 
joint often with two pectinate bristles; no eyes; legs I 
ending in several long hairs; adult sometimes parasitic 
.CHEYLETIDiE 

Cheyletus eruditus, which frequents old books, has once 
been found in pus discharged from the ear of man. 
hh. Palpi less thickened, moving vertically; eyes usually present; 
leg I not ending in long hairs. 

i. Coxae contiguous, radiate; legs slender, bristly; body with 

few hairs; no dorsal groove; tarsi not swollen . 

. Erythr.eid.e. 

ii. Coxae more or less in two groups; legs less bristly. 












272 


Hominoxious Arthropods 



158. (a) Tydeus, beak and leg from below; (b) Cheyletus pyriformis, beak and palpus: 

(c) beak and claw of Pediculoides; ( d) leg of Sarcoptes; (e) scutum of 
female of Amblyomma americana; (/) leg i and tip of mandible of Histio- 
stoma americana; (g) Histiogaster malus, mandible and venter; ( h ) Aleuro- 
bius farinae, and leg i of male: (*) Otodectes cynotis. tip of abdomen of male, 
(j) beak and anal plate of Dermanyssus gallinae; ( k ) palpus of Allothrom- 
bium. (a) to (j) after Banks. 





















A carina 


273 


j. Body with fewer, longer hairs; often spinning threads; 
no dorsal groove; tarsi never swollen; mandibles 

styhform (for piercing). TETRANYCHID® 

The genus Tetranychus may be distinguished from the 
other genera occurring in the United States by the 
following characters: No scale-like projections on 
the front of the cephalothorax; legs I as long or 
longer than the body; palp ends in a distinct thumb; 
the body is about 1.5 times as long as broad. T. 
molestissimus Weyenb. from South America, and 
T. telarius from Europe and America ordinarily 
infesting plants, are said also to molest man. 
jj. Body with many fine hairs or short spines; not spinning 
threads; often with dorsal groove; tarsi often 
swollen. 

k. Mandibles styliform for piercing. . . . Rhycholophid.-e. 

kk. Mandibles chelate, for biting. TROMBIDID® 

The genus Trombidium has recently been sub¬ 
divided by Berlese into a number of smaller 
ones, of which some five or six occur in the 
United States. The mature mite is not para¬ 
sitic but the larvae which are very numerous in 
certain localities will cause intense itching, 
soreness, and even more serious complications. 
They burrow beneath the skin and produce 
inflammed spots. They have received the 
popular name of “red bug,” The names Leptus 
americanus and L. irritans have been applied to 
them, although they are now known to be im¬ 
mature stages. (Fig. 44.) 

HEXAPODA (Insecta) 

The Thysanura (springtails and bristletails), the Neuropteroids 
(may-flies, stone-flies, dragon-flies, caddis-flies, etc.), Mallophaga 
(bird lice), Phvsopoda (thrips), Orthoptera (grasshoppers, crickets, 
roaches), are of no special interest from our viewpoint. The remain¬ 
ing orders are briefly characterized below. 

SIPHUNCULATA (page 275) 

Mouth parts suctorial; beak fleshy, not jointed; insect wingless; 
parasitic upon mammals. Metamorphosis incomplete. Lice. 

HEMIPTERA (page 275) 

Mouth parts suctorial; beak or the sheath of the beak jointed; 
in the mature state usually with four wings. In external appearance 




274 


Hominoxious Arthropods 


the immature insect resembles the adult except that the immature 
form (i. e. nymph) never has wings, the successive instars during 
the process of growth, therefore, are quite similar; and the meta¬ 
morphosis is thus incomplete. To this order belong the true bugs, 
the plant lice, leaf hoppers, frog hoppers, cicadas, etc. 

LEPIDOPTERA 

The adult insect has the body covered with scales and (with the 
rare exception of the females of a few species) with four wings also 
covered with scales. Proboscis, when present, coiled, not seg¬ 
mented, adapted for sucking. Metamorphosis complete, i.e. the 
young which hatches from the egg is quite unlike the adult, and after 
undergoing several molts transforms into a quiescent pupa which is 
frequently enclosed in a cocoon from which the adult later emerges. 
The larvae are known as caterpillars. Butterflies and moths. 

DIPTERA (page 285) 

The adult insect is provided with two, usually transparent, 
wings, the second pair of wings of other insects being replaced by a 
pair of halteres or balancers. In a few rare species the wings, or 
halteres, or both, are wanting. The mouth parts, which are not 
segmented, are adapted for sucking. The tarsi are five-segmented. 
Metamorphosis complete. The larva?, which are never provided 
with jointed legs, are variously known as maggots, or grubs, or 
wrigglers. Flies, midges, mosquitoes. 

SIPHONAPTERA (page 316) 

Mouth parts adapted for sucking; body naked or with bristles 
and spines; prothorax well developed; body compressed; tarsi 
with five segments; wings absent. Metamorphosis complete. 
The larva is a wormlike creature. Fleas. 

COLEOPTERA 

Adult with four wings (rarely wanting), the first pair horny or 
leathery, veinless, forming wing covers which meet in a line along 
the middle of the back. Mouth parts of both immature stages and 
adults adapted for biting and chewing. Metamorphosis complete. 
The larvae of many .species are known as grubs. Beetles. 


Siphunculata and Hemiptera 


2 75 


HYMENOPTERA 

Adult insect with four, usually transparent, wings, wanting in 
some species. Mouth parts adapted for biting and sucking; palpi 
small; tarsi four or five-segmented. Metamorphosis complete. 
Parasitic four-winged flies, ants, bees, and wasps. 

SIPHUNCULATA AND HEMIPTERA 

a. Legs with claws fitted for clinging to hairs; wings wanting; spiracles of the 

abdomen on the dorsal surface. ( = ANOPLURA = PARASITICA). 

.SIPHUNCULATA. 

b. Legs not modified into clinging hooks; tibia and tarsus very long and 
slender; tibia without thumb-like process; antennae five-segmented 

.H^matomyzid.e Endr. 

Hczmatomyzus elephantis on the elephant, 
bb. Legs modified into clinging hooks; tibia and tarsus usually short and 
stout; tibia with a thumb-like process; head not anteriorly pro¬ 
longed, tube-like. 

c. Body depressed; a pair of stigmata on the mesothorax, and abdominal 
segments three to eight; antennae three to five-segmented, 

d. Eyes large, projecting, distinctly pigmented; pharynx short and 
broad; fulturae (inner skeleton of head) very strong and broad, 
with broad arms; proboscis short, scarcely attaining the thorax. 

.PEDICULIDiE 

e. Antenna; three-segmented. A few species occurring upon old 

world monkeys. Pedicinis Gerv. 

ee. Antennae five -segmented. 

f. All legs stout; thumb-like process of the tibia very long and 
slender, beset with strong spines, fore legs stouter than the 
others; abdomen elongate, segments without lateral pro¬ 
cesses; the divided telson with a conical process posteriorly 

upon the ventral side.Pediculus L. 

g. Upon man, 

h. Each abdominal segment dorsally with from one to three 
more or less regular transverse rows of small setae; 
% antenna about as long as the width of the head. Head 

louse (fig. 65).P. humanus. 

hh. “No transverse rows of abdominal setae; antenna longer 
than the width of the head; species larger.” Piaget. 

Body louse of man.P. corporis. 

gg. Upon apes and other mammals. P. pusitatus (?). 

ff. Fore legs delicate, with very long and slender claws; other legs 
very stout with short and stout claws; thumb-like process of 
the tibia short and stout; abdomen very short and broad; 
segment one to five closely crowded, thus the stigmata of seg¬ 
ments three to five apparently lying in one segment; segments 
five to eight with lateral processes; telson without lateral 

conical appendages (fig. 69). Crab louse of man . 

.Phthirus pubis. 













276 


Hominoxious Arthropods 


dd. Eyes indistinct or wanting; pharynx long and slender, fulturae very 
slender and closely applied to the pharynx; proboscis very long. 

Several genera found upon various mammals. H;ematopinid.;e. 

cc. Body swollen; meso- and metathorax, and abdominal segments two to 
eight each with a pair of stigmata; eyes wanting; antennae four or 
five-segmented; body covered with stout spines. Three genera found 

upon marine mammals. Echinophthiriid^e 

aa. Legs fitted for walking or jumping; spiracles of abdomen usually ventral; 
beak segmented. 

b. Apex of head usually directed anteriorly; beak arising from its apex; sides 
of the face remote from the front coxae; first pair of wings when present 
thickened at base, with thinner margins.HETEROPTERA 



c. Front tarsi of one segment, spade-form (pakeformes); beak short, at 
most two-segmented; intermediate legs long, slender; posterior pair 

adapted for swimming.CoRixiDiE 

ec. Front tarsi rarely one-segmented, never spade-form; beak free, at least 
three-segmented, 

d. Pulvilli wanting. 

e. Hemelytra usually with a distinct clavus (fig. 159), clavus always 
ends behind the apex of the scutellum, forming the commissure. 
(Species having the wings much reduced or wanting should be 
sought for in both sections.) 

f. Antenna; very short; meso- and metasternum composite; eyes 
always present. 


















Siphunculata and Hemiptera 


277 


g. Ocelli present; beak four-segmented. Ochterid/E and 
Nerthrioe. 

gg. Ocelli wanting; antennae more or less hidden in a groove, 

h. Anterior coxae inserted at or near anterior margin of the 
prostemum; front legs raptorial; beak three-segmented. 
Belostomid^e (withswimming legs), Nepid/e, Naucorid.e. 

i. Metasternum without a median longitudinal keel; antennae 
alw'ays four -segmented. 

j. Beak short, robust, conical; the hairy fleck on the corium 
elongate, large, lying in the middle between the inner 
angle of the membrane and the outer vein parallel to 
the membrane margin; membrane margin S-shaped. 

k. The thick fore femur with a relatively deep longitudinal 
furrow to receive the tibia. Several American 
species (fig. 19f.). . .Belostoma ( = Lethocerus Mayer) 
kk. The less thickened fore femur without such a furrow 

.B. griseus. Benacus Stal. 

jj. Beak slender, cylindrical; the hairy spot on the corium 
rounded lying next to the inner angle of the membrane, 
k. Membrane large, furrow of the embolium broadened. 


Z. aurantiacum, fluminea, etc. Zaitha 

kk. Membrane very short; furrow of embolium not 
broadened. Western genus. Pedinocoris 


ii. Metasternum with a long median longitudinal keel. South¬ 
western forms. A bedus ovatus and Deniostoma dilatato 

hh. Anterior coxae inserted at the posterior margin of the 
prosternum; legs natatorial. Back swimmers (fig. 19 b.) 
. NOTONECTIDjE 

i. Apices of the hemelytra entire; the three pairs of legs 

similar in shape; beak three-segmented; abdomen not 
keeled or hairy. Plea Leach 

ii. Apices of hemelytra notched; legs dissimilar; beak four- 

segmented; abdomen keeled and hairy, 
j. Hemelytra usually much longer than the abdomen; 
fourth segment of the antenna longer than the third 

segment; hind tarsi with claws . Bueno Kirk. 

jj. Hemelytra but little longer than the abdomen; fourth 
segment of the antenna shorter than the third seg¬ 
ment; hind tarsi without claws (fig. 19b). . Notonecta L. 
ff. Antennae longer than the head; or if shorter, then the eyes and 
ocelli absent. 

g. Eyes, ocelli, and scutellum wanting; beak three-segmented; 
head short; hemelytra always short; membrane wanting. 

Insects parasitic on bats. Polyctenid.e 

gg. Eyes present. 

h. First tw r o antennal segments very short, last two long, pilose, 
third thickened at the base; ocelli present, veins of the 
hemelytra forming cells. Dipsocorid.e ( = Ceratocombi- 
d.e) including Schizopterid.e. 










Hominoxious A rthropods 


hh. Third segment of the antenna not thickened at the base, 
second as long or longer than the third, rarely shorter, 

i. Posterior coxae hinged (cardinate), if rarely rotating, the 
cuneus is severed, the membrane is one or two-celled, 
and the meso- and metastemum are composite, 

j. Ocelli absent, clypeus dilated toward the apex; hemelvtra 
always short, membrane wanting. Species parasitic. 

Bed bugs, etc. ClMlClDiE 

k. Beak short, reaching to about the anterior coxae; 
scutellum acuminate at the apex; lateral margin of 
the elytra but little reflexed, apical margin more or 
less rounded; intermediate and posterior coxae 
very remote. 

1 . Body covered with short hairs, only the sides of the 
pronotum and the hemelytra fringed with longer 
hairs; antennae with the third and fourth seg¬ 
ments very much more slender than the first and 
second; pronotum with the anterior margin very 

deeply sinuate .Cimex L. 

m. Sides of the pronotum widely dilated, broader 
than the breadth of one eye, and densely 
fringed with backward curved hairs; apical 
margin of the hemelytra nearly straight, rounded 
toward the interior or exterior angles, 

n. Body covered with very short hairs; second 
segment of the antenna shorter than the third; 
sides of the pronotum feebly reflexed, fringed 
with shorter hairs than the breadth of one 
eye; hemelytra with the commissural (inner) 
margin rounded and shorter than the scutel¬ 
lum, apical margin rounded towards the 
interior angle. The common bed bug (fig. 

19I1).C. lectularius Linn 

nn. Body covered with longer hairs; second and 
third segments of the antenna of equal 
length; side of the pronotum narrowly, but 
distinctly, reflexed, fringed with longer 
hairs than the breadth of one eye; hemelytra 
with the commissural margin straight and 
longer than the scutellum, apical margin 
rounded towards the exterior angle. Species 
found on bats in various parts of the United 

States. C. pillosellus Hov. 

mm. Sides of the pronotum neither dilated, nor 
reflexed, fringed with less dense and nearly 
straight hairs; hemelytra with the apical 
margin distinctly rounded. Parasitic on 
man, birds and bats. Occurs in the old 

world, Brazil and the West Indies .. . 

. C. hemipterus Fabr. ( = rotundatus) 








Siphunculata and Hemiptera 


279 


11 . Body clothed with rather longer silky hairs; third 
and fourth segments of the antenna somewhat 
more slender than the first and second; anterior 
margin of the pronotum very slightly sinuate or 
nearly straight in the middle, produced at the 
lateral angles. This is the species which in Ameri¬ 
can collections is known as C. hirundinis, the 
latter being an old world form. It is found in 
swallow's nests. O. vicarius. .. Oeciacus Slal 
kk. Beak long, reaching to the posterior coxas; scutellum 
rounded at the apex; lateral margins of the elytra 
strongly reflexed, apical margin slightly sinuate 
tow'ard the middle; intermediate and posterior 
coxae sub-contiguous. This species infests poultry 
in southwest United States and in Mexico. H. 
inodorus.Haematosiphon Champ. 



160. Pselliopsis (Milyas) 
cinctus. (x 2 ). After 
C. V. Riley. 


jj. Ocelli present, if rarely absent in the female, then the 
tarsus has two segments; or if with three tarsal seg¬ 
ments, the wing membrane with one or two cells, 
k. Beak four-segmented, or with tw'o-segmented tarsi. 

. .Isometopid^e, Microphysid.e and some Capsids. 
kk. Beak three-segmented. 

I . Hemelytra with embolium; head horizontal, more 

or less conical; membrane with one to four veins, 

rarely W'anting.ANTHOCORIDjE 

Several species of this family affecting man have 
been noted, Anthocoris kingi and congolense, 
from Africa and Lyctocoris campestris from 
various parts of the world. Lyctocoris fitchii 
Reuter (fig. 19 j), later considered by Reuter as 
a variety of L. campestris, occurs in the United 
States. 

II . Hemelytra wdthout embolium. Superfamily Acan- 

thioidea ( = Sald^e Fieber and Leptopod.e 
Fieber) 





2So 


Hominoxious Arthropods 


ii. Posterior coxa; rotating. 

j. Claws preapical; aquatic forms. Gerrid® and Veliad® 
jj. Claws apical. 

k. Prosternum without stridulatory sulcus (notch for 
beak). 

I. Tarsus with three segments; membrane with two or 

three longitudinal cells from which veins radiate; 
rarely with free longitudinal veins (Arachnocoris) 
or veins nearly obsolete (Arbela); clavus and 
corium coriaceous; ocelli rarely absent. . Nabid® 
Reduviolus ( = Coriscus) subcoleoptratus (fig. 19 g), 
a species belonging to this family, occurring in 
the United States, has been accused of biting 
man. This insect is flat, of a jet black color, 
bordered with yellow on the sides of the abdomen, 
and with yellowish legs. It is predaceous, 
feeding on other insects. 

II. With other combinations of characters. Hydro- 

METRID®, HENICOCEPHALID®, N®OGEID®, MESO- 
VELIAD®, JOPPEICID® 

kk. Prosternum with stridulatory sulcus (notch for beak); 
with three segments, short, strong. 

I. Antennae filiform or sometimes more slender apically, 

geniculate; wing membrane with two or three 
large basal cells; scutellum small or moderate 

.REDUVIID® 

For a key to the genera and species see next page. 

II. Last antennal segment claVhte or fusiform; wing 

membrane with the veins often forked and ana¬ 
stomosing; scutellum large; tarsi each with two 
segments; fore legs strong. ( = Phy t matid®) 

. Macrocephalid.e 

ee. Clavus noticeably narrowed towards the apex, never extending 
beyond the scutellum, the two not meeting to form a commissure; 
head horizontal, much prolonged between the antennse, on each 
side with an antennal tubercle, sometimes acute; ocelli absent; 
meso- and metasternum simple; tarsi each with two segments; 
body flattened (fig. 19c). Aradid®, including Dysodiid®. 
dd. Pulvilli present (absent in one Australian family THAuM atocorid ® 
in which case there is a membranous appendage at the tip of the 
tibia). Capsid.® ( = Mirid®),* Eotrechus (in family Gerrid®), 
N®ogaid®, Tingitid®, Piesmid®, Myodochid®, Corizid®, 
Coreid®, Alydid®, Pentatomid®, Scutellerid®, etc. 
bb. Apex of head directed ventrally, beak arising from the hinder part of the 
lower side of the head; sides of face contiguous to the front coxae; first 


*Professor C. R. Crosby who has been working upon certain capsids states that he and his 
assistant have been bitten by Lygus pratensis, the tarnished plant bug, by Chlamydatus associatus 
and by Orthotylus flavosparsus, though without serious results. 





Reduviidce of the United States 


281 


pair of wings, when present, of uniform thickness. Cicadas, scale 
insects, plant lice (Aphids), spittle-insects, leaf hoppers, etc . 


HOMOPTERA 


ReduvtidjE of the United States 

(Adapted from a key given by Fracker). 

a. Ocelli none; wings and hemelytra always present in the adults; no discodial 
areole in the corium near the apex of the clavus. Orthometrops decor ata, 

Oncerotrachelus acuminatus, etc., Pennsylvania and south. Sarcince 

aa. Ocelli present in the winged individuals; anterior coxae not as long as the 
femora. 

b. Hemelytra without a quadrangular or discoidal areole in the corium near 
the apex of the clavus. 

c. Ocelli not farther cephalad than the caudal margins of the eyes; segment 
two of the antenna single. 

d. Thorax usually constricted caudad of the middle; anterior coxae ex¬ 
ternally flat or concave . PIRATING 

e. Middle tibiae without spongy fossa, head long, no lateral tubercle 

on neck. S. stria, Carolina, Ill., Cal . Sirthenia Spinola 

ee. Middle tibiae with spongy fossa; fore tibiae convex above; neck 
with a small tubercle on each side, 

f. Apical portion of anterior tibiae angularly dilated beneath, the 

spongy fossa being preceded by a small prominence. 

. Melanolestes Stal 

g. Black, with piceous legs and antennae. N. E. States (fig. 19a) 

. M. picipes 

gg. Sides, and sometimes the whole dorsal surface of the abdomen 

red. Ill., and southward. M. abdominalis 

ff. Tibiae not dilated as in “f”; spongy fossa elongate; metapleural 
sulci close to the margin. R. biguttatus (fig. 22). South 

. Rasahus A. and S. 

dd. Thorax constricted in the middle or cephalad of the middle; anterior 
tarsi each three-segmented. 

e. Apex of the scutellum narrow, without spines or with a single spine 

. REDUVIINjE 

f. Antennae inserted in the lateral or dorso-lateral margins of the head; 
antenniferous tubercles slightly projecting from the sides of the 
head; head produced strongly cephalad; ocelli at least as far 
apart as the eyes. 

g. Antennae inserted very near the apex of the head; segments 
one and three of the beak short, segment two nearly four 

times as long as segment one. R. prolixus. W. I . 

. Rhodnius Stal 

gg. Antennae inserted remote from the vertex of the head. 

h. Body slightly hairy; pronotum distinctly constricted; angles 
distinct; anterior lobe four-tuberculate, with the middle 
tubercles large and conical. M. phyllosoma, large species 
the southwest. Meccus Stal 
















282 


Hominoxious Arthropods 


hh. Body smooth, margin of the pronotum sinuous, scarcely 
constricted; anterior lobe lined with little tubercles 
. Conorhinus Lap. 

i. Surface of the pronotum and prosternum more or less 

grandular. 

j. Eyes small, head black; body very narrow, a fifth as 

wide as long; beak reaches the middle of the proster¬ 
num. California . C. protractus 

jj. Eyes large, head fuscous; body at least a fourth as wide 

as long. Southern species . C. mbro f asciatus 

ii. Pronotum and prosternum destitute of granules. 

j. Border of abdomen entirely black except for a narrow 
yellowish spot at the apex of one segment. Texas 

. C. gerstaeckeri 

jj. Border of abdomen otherwise marked. 

k. Beak slender, joints one and two slightly pilose, two 
more than twice as long as one; tubercles at the 
apical angles of the pronotum slightly acute, conical. 
Md. to Ill. and south. The masked bed bug hunter 

(fig. 71) . C. sanguisugus 

kk. Beak entirely pilose, joint two a third longer than 
joint one; joint one much longer than three; 
tubercles at the apical angles of pronotum slightly 
elevated, obtuse. Ga., Ill., Tex., Cal. . C. variegatus 
ff. Antenna inserted on top of the head between margins, close to the 
eyes; antenniferous tubercles not projecting from the side of the 
head. 

g. Anterior lobe of the pronotum with a bispinous or bituberculate 
disc; femora unarmed. S. arizonica, S. bicolor. South¬ 


western species. Spiniger Burm. 

gg. Disc of pronotum unarmed; apex of scutellum produced into 
a spine; ocelli close to the eyes; eyes large and close to¬ 
gether . Reduvius Lamarck 

h. Color piceous. Widely distributed' in the United States. 

(Fig. 20). R. personatus 

hh. More or less testaceous in color. Southwestern states 
.R. senilis 


ee. Apex of scutellum broad, with two or three spines. . Ectrichodiin.® 
f. First segment of the antenna about as long as the head. E. cruciata 

Pa. and south; E. cinctiventris, Tex. and Mex . 

. Ectrichodia L. et S. 

ff. First segment of the antennae short. P. ceneo-nitens. South 

. Pothea A. et S. 

cc. Ocelli cephalad of the hind margins of the eyes; first segment of the 
antennae stout, second segment divided into many smaller segments. 
South and west. Homalocoris maculicollis, and Hammatocerus 
purcis . HammatoceriNjE 















Reduviidce of the United States . 283 

bb. Hemelytra with a quadrangular or discoidal areole in the corium near the 
apex of the clavus (fig. 159c). 

c. Anal areole of the membrane not extending as far proximad as the costal 
areole; basal segment of the antenna thickened, porrect; the other 
segments slender, folding back beneath the head and the first segment 

. Stenopodin\e 

d. Head armed with a ramous or furcate spine below each side, caudad 
of the eyes. 

e. First segment of the antenna thickened, apex produced in a spine 
beyond the insertion of the second segment. Species from Va., 

Ill. and south . Pnirontis Stal. 

ee. First segment of the antenna not produced beyond the insertion 
of the second segment. Pygolampis, N. E. states and south; 
Gnathobleda, S. W. and Mex. 

dd. Head unarmed below or armed with a simple spine; rarely with a 
subfurcate spine at the side of the base. Carolina, Missouri and 
south. Slehopoda, Schumannia , Diaditus, Narvesus, Oncocephalus 
cc. Anal areole of membrane extending farther proximad than the costal 
areole. 

d. Ocelli farther apart than the eyes. A. crassipes, widely distributed 

in the United States; other species occur in the southwest . 

. Apiomerus Hahn. 

dd. Ocelli not so far apart as the eyes. Zelin^e 

e. Sides of mesosternum without a tubercle or fold in front. 

f. Fore femur as long as or longer than the hind femur; first segment 
of the beak much shorter than the second. Z. audax, in the 
north eastern states; other species south and west. .Zelus Fabr. 
ff. Fore femur shorter than the hind femur, rarely of equal length, 
in this case the first segment of the beak as long or longer than 
the second. 

g. First segment of the beak shorter than the second; fore femur 
a little shorter than the hind femur; the first segment of the 
beak distinctly longer than the head before the eyes. P. 
cinctus a widely distributed species (fig. 160). P. punctipes , 

P. spinicollis, Cal., Mex.(= Mityas) Pselliopus Berg. 

gg. First segment of the beak as long or longer than the second, 

h. Pronotum armed with spines on the disc. 

i. Juga distinctly prominent at the apex and often acute or 

subacute; fore femur distinctly thickened; hemelytra 
usually not reaching the apex of the abdomen. Fitchia 
aptera, N. Y., south and west; F. spinosula, South; 
Rocconata annulicornis, Texas, etc. 

ii. Juga when prominent, obtuse at apex; eyes full width of 

the head; fore femur not thickened; pronotum with four 
spines on posterior lobe. R. tanrus, Pa., south and west 

. Repipta Stal. 

hh. Pronotum unarmed on the disc. 









284 


Hominoxious A rthropods 


i. Spines on each apical angle of the penultimate abdominal 

segment. A. cinereus, Pa., and south. . Atrachelus A. et S. 

ii. Apical angle of the penultimate abdominal segment un¬ 

armed. Fitchia (in part); Castolus *erox, Arizona, 
ee. Sides of the mesosternum with a tubercle of fold in front at the hind 
angles of the prosternum; first segment of the beak longer than 
the part of the head cephalad of the eyes, 
f. Fore femur thickened, densely granulated; hind femur unarmed. 



161. Taxonomic details of Diptera. (a) Ventral aspect of abdomen of Cynomyia; 

( b ) antenna of Tabanus; (c) ventral aspect of abdomen of Choitophila; (d) 
ventral aspect of abdomen of Stomoxys; ( e ) claw of Aedes (Culex) sylves- 
tris, male; (f) claw of Hippoboscid; ( g ) foot of dipterous insect showing 
empodimm developed pulvllliform; {h) hind tarsal segment of Simulium 
vittatum, female; (*) foot of dipterous insect showing bristle-like empodium. 

g. Fore tibiae each with three long spines on the ventral side. 
S. diadema (fig. I59e), a widely distributed species; and 

several southwestern species. Sinea A. et S. 

gg. Fore tibiae unarmed. A. multispinosa, widely distributed; 

A. tabida, Cal. Acholla Stal. 

ff. Fore femur unarmed, rarely a little thickened, a little granulated, 
g. Pronotum produced caudad over the scutellum, with a high 
mesal tuberculate ridge (fig. 19c). A. cristatus. N. Y. to 

Cal. and south.Arilus Hahn. 

gg. Caudal lobe of the pronotum six sided, neither elevated nor 
produced caudad. H. americanus, Southwest; also several 
W. I. and Mexican genera.Harpactor Lap. 













Dipt era 285 

DIPTERA (Mosquitoes, Midges, Flies) 

a. Integument leathery, abdominal segments indistinct; wings often wanting; 

parasitic forms.PUPIPARA 

b. Head folding back on the dorsum of the thorax; wingless flies parasitic 

on bats. Genus Nycteribia . Nycteribiid^: 

bb. Head not folding back upon the dorsum of the thorax; flies either winged 
or wingless; parasitic on birds and on bats and other mammals, 

c. Antennae reduced, wings when present, with distinct parallel veins and 
outer crossveins; claws simple; palpi leaf-like, projecting in front of 
the head. Flies chiefly found on bats. Several genera occur in North 
America . Streblid^e 



162. Hippobosca equina, xq. After Osborn. 


cc. Antennae more elongate, segments more or less distinctly separated; 
head sunk into an emargination of the thorax; wings when present 
with the veins crowded toward the anterior margin; palpi not leaf¬ 
like . HlPPOBOSCIDAs 

d. Wings absent or reduced and not adapted for flight. 

e. Wings and halteres (balancers) absent. M. ovinus, the sheep tick 

. Melophagus Latr. 

ee. Wing reduced (or cast off), halteres present. 

f. Claw bidentate; ocelli present. On deer after the wings are cast 

off. L. depressa . Lipoptena Nitsch 

ff. Claw tridentate (fig. 161 f).On Macropis. B. femorata 

. Brachypteromyia d Will. 

dd. Wings present and adapted for flight, 
e. Claws bidentate. 

f. Ocelli present; head flat; wings frequently cast off. On birds 

before casting of the wing . Lipoptena Nitsch. 

ff. Ocelli absent; head round; wings present. The horse tick 

H. equina may attack man (fig. 162) . Hippobosca L. 

ee. Claws tridentate (fig. 161 f.). 
f. Anal cell closed at apical margin by the anal crossvein. 

g. Ocelli absent . Stilbometopa Coq. 

gg. Ocelli present. 












286 


Hominoxious Arthropods 


h. R4+5 does not form an angle at the crossvein. On birds. 
There is a record of one species of this genus attacking man 

.Omithomyia Latr. 

hh. R4+5 makes an angle at the crossvein. O. confluens. 

. Ornithoica Rdi. 

ff. Anal cell not closed by an anal crossvein. Lynchia, Pseudolfersia, 
and Olfersia are chiefly bird parasites. The first mentioned 
genus is said to be the intermediate host of Hcemoproteus columbce. 
aa. Abdominal segments chitinous; not parasitic in the adult stage. 

b. Antennae with six or more segments and empcdium not developed pulvilli- 
form; palpi often with four segments, 
c. Ocelli present. Blepharocerid.*, Rhyphid^e, Bibionim:, Myceto- 
philid/E, besides some isolated genera of other families, 
cc. Ocelli absent. 

d. Dorsum of the thorax with a V-shpaed suture; wings usually with 
numerous veins; legs often very long and slender. Crane flies. 

. TlPULID/E 

dd. Dorsum of the thorax without a V-shaped suture. 

e. Not more than four longitudinal veins ending in the wing margin; 
w T ing usually hairy: antennae slender; coxae not long; tibiae with¬ 
out spurs, legs long and slender. Small, delicate flies often called 

Gall gnats. Cecidomyiid/E 

ee. More than four longitudinal veins ending in the wing margin, 

f. The costal vein is not produced beyond the tip of the wing; radius 
with not more than three branches, 

g. Antennae short, composed of ten or eleven closely united seg¬ 
ments; legs stout; body stout; abdomen oval; anterior 
veins stout, posterior ones weak (fig. 163 b); eyes of the male 
contiguous over the antennae. Black flies, buffalo flies, 

turkey gnats. Many North American species, several of 

them notorious for their blood sucking propensities. 

.SlMULIIDiE 

h. Second joint of the hind tarsus with basal scale-like process and 
dorsal excision (fig. 161 h); radial sector not forked; no 
small cell at the base of the wing. S. forbesi, jenningsi, 
johannseni, meridionale, piscicidium, venustum, vittatum, 

etc. Widely distributed species. 

.( = Eusimulium) Simulium Latr. 

hh. No basal scale-like process on the second joint of the hind 
tarsus; radial sector usually forked (fig. 163 b). 

i. Face broad, small basal cell of the wing present. P. fulvum, 

hirtipes, mutalum, pecuarum, pleurale. . Prosimulium Roub. 

ii. Face linear; small basal cell of the wing absent. One 

species, P. furc'atum, from California. 

. Parasimulium Malloch 

gg. Flies of a different structure. 

h. Antennas composed of apparently two segments and a terminal 
arista formed of a number of closely united segments. 
Rare flies with aquatic larvae . Orphnephilid.e 













Diptera 


287 

hh. Antennae of six to fifteen segments, those of the male usually 
plumose; legs frequently slender and wings narrow 

. CHIRONOMIDiE 

i. Media forked (except in the European genus Brachypogon ) ; 
thorax without longitudinal fissure and not produced over 
the head (except in four exotic genera); antennae usually 
fourteen-jointed in both sexes; fore tibia with a simple 
comb of setulae, hind tibia with two unequal combs, 

middle tibia without comb. CeratopogoniNjE 

j. Thorax produced cap-like over the head, wing narrow 
and very long. Jenkinsia, Macroptilum and Caly- 
ptopogon, eastern hemisphere; Paryplioconiis, Brazil, 
jj. Thorax not produced over the head. 

k. Eyes pubescent, empodium well developed, or if short 
then R2+3 distinct and crossvein-like or the 
branches of R coalescent; r-m crossvein present; 
fore femora not thickened; wing either with ap- 
pressed hairs or with microscopic erect setulae 

. Dasyhelea Kieff. 

kk. Eyes bare, or otherwise differing from the foregoing. 

I . Empodium well developed, nearly as long as the 

claws and with long hairs at the base; femora and 
fifth tarsal segments unarmed, i.e. without spines 
or stout setae; fourth tarsal segment cylindrical, 

m. Wing with erect and microscopic setulae. Widely 

distributed. 

.(= Atrichopogon) Ceratopogon Meig. 

mm. Wing with long and depressed hairs. Widely 

distributed . Forcipomyia 

n. Hind metatarsus shorter or not longer than the 
following (i.e. the second tarsal) segment 

. Subgenus Prohelea Kieff 

nn. Hind metatarsus longer than the following 
segment .... Subgenus Forcipomyia Meig. 

II . Empodium short, scarcely reaching the middle of 

the claws, or vestigial, 
m. R-m crossvein wanting. 

n. Palpi four segmented; inferior fork of the media 

obliterated at the base. Australia . 

. Leptoconops Skuse 

nn. Palpi three-segmented. 

o. Legs spinulose, tarsal claws of the female 
with a basal tooth or strong bristle, those 
of the male unequal, the anterior with a 
long sinuous tooth, the posterior with a 

short arcuate tooth. Italy . 

. Mycterotypus No£ 













Horn inoxious A rthropods 


oo. Legs unarmed; no crossvein between the 
branches of the radius (fig. 163c). New 

Mexico . Tersesthes Townsend 

mm. R-m crossvein present. 

n. Fore femora very much swollen, armed with 
spines below, fore tibia arcuate and applied 
closely to the inferior margin of the femur, 

o. R2+3 present, therefore cell R x and R 2 both 
present; wing usually fasciate. United 

States. Heteromyia Say. 

00. R2+3 not distinct from R4 + 5, hence cell 

R3 obliterated. South America. 

. Pachyleptus Arrib. (Walker) 

nn. Fore femur not distinctly swollen. 

o. R 2 + 3 present therefore cells Ri and R 3 
both present, or if not, then the branches 
of the radius more or less coalescent, 
obliterating the cells. 

p. At least the tip of the wing with erect 
setulae; tip of R4+5 scarcely attaining 
the middle of the wing, empodium rather 
indistinct, not reaching the middle of the 
claws, the claws not toothed, equal, with 
long basal bristle; legs without stout 

setae. Widely distributed. 

.Culicoides Latr. 

Haematomyidium and Oecacta are prob¬ 
able synonyms of this, 
pp. Wings bare, if rarely with hair, then the 
radius reaches beyond two-thirds the 
length of the wing, or the femur or 
fifth tarsal segment with stout black 
spines. 

q. Media unbranched. Europe . 

. Brachypogon Kieff 

qq. Media branched. 

r. Hind femur much swollen and spined. 

America and Europe. Serromyia Meg. 
rr. Hind femur not distinctly swollen, 

s. Cell Rj not longer than high; fork 
of the media distad of the cross¬ 
vein; wing with microscopic setu¬ 
lae . Stilobezzia Kieff 

ss. Cell R r elongate. 

t. Femora unarmed. Widely dis¬ 
tributed. (= Sphaeromias Kieff. 

1913 not Curtis?) . 

.Johannseniella Will. 













Dipt era 


289 


tt. Femora, at least in part, with 
strong black spines. Widely 
distributed. Palpomyia Megerle 
00. R2+3 coalescent with R4+5 hence cell Ra 
is obliterated. 

p. In the female the lower branch of the 
media with an elbow near its base pro¬ 
jecting proximad, the petiole of the 
media coalescent with the basal section 
of the radius, wing long and narrow, 
radial sector ending near the tip of the 
wing; venation of the male as in Bezzia\ 

front concave. United States. 

. Stenoxenus Coq. 

pp. Venation otherwise, front not concave, 
q. Subcosta and Ri more or less coalescent 
with the costa; wing pointed at the 
apex, much longer than the body; 
antennas fourteen segmented, not plu¬ 
mose. India. Haasiella Kieff. 

qq. Subcosta and radius distinct from the 
costa. 

r. Abdomen petiolate... Dibezzia Kieff. 
rr. Abdomen not petiolate. 

s. Head semi-globose; hind tarsi un¬ 
usually elongate in the female; 
antennas of the male not plumose. 

Europe. Macropeza Meigen. 

ss. Head not globose, more or less 

flattened in front; antennae of 
the male plumose. Widely dis¬ 
tributed . Bezzia Kieff. 

t. Fore femora, at least, armed with 

stout spines below r . 

.Subgenus Bezzia Kieff. 

tt. Femora unarmed. 

.... Subgenus Probezzia Kieff. 
ii. Media of the wing simple, and otherwise not as in “i”. To 
this group belong numerous Chironomid genera, none of 
which are known to be noxious to man. 
ff. The costal vein apparently is continued around the hind margin of 
the wing; radius with at least four branches, 
g. Wing ovate pointed, with numerous veins; crossveins, if evi¬ 
dent, before the basal third of the wing; veins very hairy; 

very small moth-like flies. PsychodiDjE 

h. With elongate biting proboscis; the petiole of the anterior 
forked cell of the wing (R 2 ) arises at or beyond the middle of 
the wing (fig. 163d).Phlebotomus Rdi. 












290 


Hominoxious Arthropods 



163. Wings of Diptera. (a) Anopheles; ( b) Prosimulium; (c) Johannseniella; (d) Phle- 
botomus (After Doerr and Russ); (e) Tersesthes (after Townsend); (/) Ta- 
banus; (g) Symphoromyia; (h) Aphiochaeta; (*') Eristalis; (J) Gastrophilus; 
( k ) Fannia; ( l) Musca. 















































Diptera 


291 


hh. With shorter proboscis; the petiole of the anterior forked 

cell arises near the base of the wing . 

. Psychoda, Pericoma, etc. 

gg. The r-m crossvein placed at or beyond the center of the wing; 
wings not folded roof-like over the abdomen, 

h. Proboscis short, not adapted for piercing; wings bare (Dixi- 
d^e); or wings scaled (CuuciDdE, Subf. CorethriNjE). 
hh. Proboscis elongate, adapted for piercing; wings scaled, 
fringed on the hind margin; antennas of the male bushy 

plumose. Mosquitoes . 

.CuliciDjE (exclusive of Corethrix^e) 

i. Metanotum without setae. 

j. Proboscis strongly decurved; body with broad, ap- 
pressed, metalescent scales; cell R 2 less than half as 
long as its petiole; claws of female simple, some of the 
claws of the male toothed. Several large southern 
species believed to feed only on nectar of flowers 

. Megarhinus R. D. 

jj. Proboscis straight or nearly so, or otherwise different, 

k. Scutellum evenly rounded, not lobed; claws simple in 
both sexes. Anopheles Meig. 

I . Abdomen with clusters of broad outstanding scales 

along the sides; outstanding scales on the veins of 
the wing rather narrow, lanceolate; upper side of 
the thorax and scutellum bearing many appressed 
lanceolate scales. Florida and southward (Cellia). 

m. Hind feet from the middle of the second segment 
largely or wholly snow white, 

n. With a black band at the base of the last seg¬ 
ment of each hind foot . 

.A. albimanus* and tarsimaculata* 

nn. Without such a band.... A. argyritarsis* 
mm. Hind feet black, mottled with whitish and with 
bands of the same color at the sutures of the 
segments. W. I . A. maculipes 

II . Abdomen without such a cluster of scales ; outstand¬ 

ing scales of the wing veins rather narrow, lanceo¬ 
late; tarsi wholly black. 

m. Deep black, thorax obscurely lined with violace¬ 
ous, especially posteriorly; head, abdomen and 
legs black; no markings on the pleura; ab¬ 
domen without trace of lighter bandings; 
wing scales outstanding, uniform, not forming 
spots, though little thicker at the usual points 
indicating the spottings. Florida. . A. atropus 

*Species marked with an * are known to transmit malaria. Species found only in tropical 
North America and not known to carry malaria have been omitted from this table, but all found 
in the United States are included. 












292 


Honiinoxious A rthropods 


mm. Otherwise marked when the wings are unspotted, 

n. Wings unspotted. 

o. Petiole of the first forked cell (R 2 ) more than a 
third the length of the cell. Mississippi 

valley.A. walkeri 

oo. Petiole of the first forked cell a third the 

length of the cell. Md . A. barberi 

nn. Wings spotted. 

o. Front margin of the wings with a patch of 
whitish and yellow' scales at a point about 
two-thirds or three-fourths of the W’ay from 
base to apex of wing. 

p. Veins of the wing with many broad obovate 
outstanding scales; thorax with a black 
dot near the middle of each side. W. I. 

.A. grabhami* 

pp. The outstanding scales of the wings rather 
narrow, lanceolate. 

q. Scales of the last vein of the wings white, 
those at each end black; R4+5 black 
scaled, the extreme apex w'hite scaled. 
Widely distributed north and south 

(fig. 131 ) .A. punctipennis 

A dark variety from Pennsylvania has 
been named A. perplexens. 
qq. Scales of the last vein of the wing white, 
those at its apex black; R4+5 w'hite 
scaled and with two patches of 
black scales. South and the tropics. 
A. franciscanus and pseudopunctipen- 
nis* 

00. Front margin of the wings wholly black 
scaled. 

p. Last (anal) vein of the wings white scaled 
with three patches of black scales (fig. 
132). New r Jersey to Texas. A. crucians* 
pp. Last vein of the w'ings wholly black 
scaled. 

q. Widely distributed north and south 

(fig. 130), (= maculipennis) . 

. A. quadrimaculatus* 

qq. Distributed from Rocky Mountains 

westward. A. occidentalis 

kk. Scutellum distinctly trilobed. 

1 . Cell R 2 less than half as long as its petiole; thorax 
with metallic blue scales; median lobe of the 
scutellum not tuberculate; few small species which 
are not common. Uranotaenia Arrib. 










Diptera 


293 


11. Cell R 2 nearly or quite as long as its petiole, or 
otherwise distinct. 

m. Femora with erect outstanding scales; occiput 
broad and exposed. Large species. P. ciliata. 

P. howardi.Psorophora R. D. 

mm. Femora without erect scales. 

n. Clypeus bearing several scales or hairs, scutel- 
lum with broad scales only; back of head 
with broad scales; scales along the sides of the 
mesonotum narrow; some or the claws 
toothed; thorax marked with a pair of 
silvery scaled curved stripes; legs black 
with white bands at the bases of some of the 
segments (fig. 134). Yellow Fever mosquito 

.Aedes ( = Stegomyia) calopus. 

nn. With another combination of characters. 
Numerous species of mosquitoes belonging 
to several closely related genera, widely 
distributed over the country'. ( Culex , Aedes, 
Ochlerotatus, etc.). Culex in the wide sense, 
ii. Metanotum with setae. Wyeomyia (found in the United 
States); and related tropic genera. 

bb. Antennae composed of three segments with a differentiated style or bristle; 
third segment sometimes complex or annulate, in which case the empo- 
dium is usually developed like the pulvilli, i.e., pad-like (fig. 161 g). 

c. Empodium developed pad-like (pulvilliform) i.e., three nearly equal 
membranous appendages on the underside of the claws (fig. i6ig). 

d. Squamae, head, and eyes large; occiput flattened or concave; third 
segment of the antennae with four to eight annuli or segments, 
proboscis adapted for piercing; body with fine hairs, never with 
bristles; middle tibia with two spurs; wing venation as figured 
(fig. i63f); marginal vein encompasses the entire wing. Horse 

flies, greenheads, deer flies, gad flies. Tabanid.®* 

e. Hind tibia with spurs at tip; ocelli usually present (PANGONIN.*) 

f. Third joint of the antennae with seven or eight segments; probo- 
cis usually prolonged. 

g. Each section the the third antennal segment branched. Central 

American species, P. festce . Pityocera G. T. 

gg. Sections of the third antennal segment not branched. 

h. Upper corner of the eyes in the female terminating in an acute 
angle; wings of both sexes dark anteriorly. G. chrysocoma, 

a species from the eastern states . Goniops Aid. 

hh. Upper comer of the eye in the female not so terminating; 
wings nearly uniform in color, or hyaline, 

i. Proboscis scarcely extending beyond the palpi; front of the 
female wide; much wider below than above. S. W. 
States . Apatolestes Will. 

*This table to the North American genera of the Tabanidffi is adapted from one given by 
M iss Ricardo. 









294 


Hominoxious Arthropods 


ii. Proboscis extending beyond the palpi. 

j. Wing with cell M3 closed. Tropic America . 

. ( = Diclisa ) Scione Wlk. 

jj. Cell M3 open; ocelli present or absent. Two or three 
eastern species; many south and west. . Pangonia Rdi. 
ff. Third segment of the antenna with five divisions; ocelli present, 

g. First and second segments of the antenna short, the second only 
half as long as the first, three western species. . . .Silvius Rdi. 
gg. First and second segments of the antenna long, the second 
distinctly over half as long as the first. Deer flies. Many 

species, widely distributed . Chrysops Meig. 

ee. Hind tibia without spurs; ocelli absent. 

f. Third segment of antenna with four divisions, no tooth or angula¬ 
tion; wings marked with rings and circles of darker coloring; 
front of the female very wide. Widely distributed. H. ameri- 

cana, H. punctulata .Hasmatopota Meig. 

ff. Third segment of the antenna with five divisions (fig. 161b). 

g. Third segment of the antenna not furnished with a tooth or 
distinct angular projection. 

h. Body covered with metallic scales; front of female of normal 
width; front and middle tibiae greatly dilated. L. 

lepidota . Lepidoselaga Macq. 

hh. Body without metallic scales; antennae not very long, the 
third segment not cylindrical, not situated on a projecting 
tubercle; front of the female narrow. South. D. 

ferrugatus . ( =Diabasis) Diachlorus 0 . S. 

gg. Third segment of the antenna furnished with a tooth or a 
distinct angular projection. 

h. Hind tibiae ciliate with long hairs. S. W. and tropics. 

. Snowiella and Stibasoma. 

hh. Hind tibiae not ciliate. 

i. Species of slender build, usually with a banded thorax and 

abdomen; third segment of the antenna slender, the 
basal prominence long; wings mostly with brownish 
markings. Tropic America . Dichelacera Macq. 

ii. Species of a stouter build; third segment of the antenna 

stout, its basal process short (fig. 161b). Many species, 

widely distributed.Tabanus L. 

dd. With another group of characters. 

e. Squamae small, antennae variable, thinly pilose or nearly bare species, 
without distinct bristles; wing veins not crowded anteriorly, R4 and 
R5 both present, basal cells large; middle tibiae at least with spurs 

. LEPTIDjE 

f. Flagellum of the antenna more or less elongated, composed of 

numerous more or less distinct divisions . 

. Xylophagin/E and Arthkoceratin.e. 

ff. Antennae short, third segment simple, with arista or style; face 
small, proboscis short .. Leptin.® 















Diptera 


295 


g. Front tibiae each with one or two spurs, or if absent, then no 
discal cell. Triptotricha, Pheneus, Dialysis, Hilarimorpha. 
gg. Front tibae without terminal spurs, discal cell present, 

h. Hind tibae each with a single spur. 

i. Anal cell open (fig. i63g); third antennal segment kidney¬ 

shaped with dorsal or subdorsal arista; first antennal 
segment elongate and thickened. About a dozen species 
have been described from the United States, of which at 
least one (S. pachyceras) is knowm to be a vicious blood 
sucker.Symphoromyia Frauenf. 

ii. Anal cell closed; third antennal segment not kidney¬ 

shaped. Chrysopila, Ptiolina, Spania. 

hh. Hind tibiae each with two spurs. 

i. Third segment kidney-shaped, the arista subdorsal; anal 

cell closed. Atherix Meig. 

ii. Third segment of the antenna short and with terminal 

arista; anal cell open. Leptis Fabr. 

Two European species of this genus have been accused of 
blood sucking habits, but the record seems to have 
been based upon error in observation. 

ee. With another combination of characters . 

. Stratiomyiid^e, Cyrtid^e, etc. 

cc. Empodium bristlelike or absent. 

d. Antennae apparently two-segmented, with three-segmented arista, 
wings (rarely wanting) with several stout veins anteriorly, the 
weaker ones running obliquely across the wing (fig. 163I1); small, 
quick running, bristly, humpbacked flies. Several genera; Aphio- 

chaeta, Phora, Trineura, etc. Phorid.® 

dd. Flies with other characters. 

e. No frontal lunule above the base of the antennae; both R4 and R5 
often present; third segment of the antenna often with a terminal 
bristle. AsiLlDiE, Mydaid.e, Apiocerid.e, Therevid^e, Sceno- 
PIMD.E, Bombyliid/E, Empidid^;, Dolichopodid.e, Lonchop- 

TERID.E. 

ee. A frontal lunule above the base of the antennae; third segment of the 
antenna always simple, i.e., not ringed, usually with a dorsal 
arista; R4 and R5 coalesced into a simple vein, 

f. A spurious vein or fold between the radius and the media, rarely 
absent; the cell R4+5 closed at the apex by vein Mi; few or no 
bristles on the body, none on the head; flies frequently with 
yellow markings. Eristalis (fig. i63i), Helophilus, and many 

other genera . SyrphiDjE 

ff. No spurious vein present. 

g. Body without bristles; proboscis elongate and slender, often 
folding; front of both male and" female broad. . . . Conopid/E 
gg. Bristles almost always present on head, thorax, abdomen and 
legs. 










296 


Hominoxious Arthropods 


h. Arista terminal; hind metatarsus enlarged, sometimes orna¬ 
mented, hind tarsus more or less flattened beneath. 

. PLATYPEZID® 

hh. Flies having a different combination of characters. 

i. Head large, eyes occupying nearly the entire head; cell 

R 4 -j- s narrowed in the margin; small flies . .Pipunculid/E 

ii. Head and eyes not unusually large. 

j. Squamae (tegulae, or calyptrae, or alulae) not large, often 
quite small, the lower one lacking, or at most barely 
projecting from below the upper one (antisquama); 
front of both male and female broad, the eyes therefore 
widely separated; posthumeral and intraalar macro- 
chaeta not simultaneously present; thorax usually 
without a complete transverse suture; postalar callus 
usually absent; the connectiva adjoining the ventral 
sclerites always visible; hypopleural macrochaetae 
absent; last section of R4+5 and Mi+o with but few 
exceptions nearly parallel; subcostal vein often wanting 
or vestigial or closely approximated to Ri; the latter 
often short, basal cells small, the posterior ones often 
indistinct or wanting; vibrissae present or absent 

. Acalyptrate muscoidea 

k. Subcosta present, distinctly separated from Ri at the 
tip; Ri usually ends distad of the middle of the 
wing; the small basal cells of the wing distinct. 

I . A bristle (vibrissa) on each side of the face near the 

margin of the mouth. Cordylurid®, Sepsid®, 
Phycodromid®, Heteroneurid®, Helomyzid®. 

II . No vibrissae present. 

m. Head nearly spherical, cheeks broad and re¬ 
treating; proboscis short; the cell R5 closed or 
narrowed in the margin; legs very long; tarsi 
shorter than the tibiae. Calobata and other 

genera . Micropezid® 

mm. Flies with another combination of characters. 
Rhopalomerid®, Trypetid®, Ortalid®, 
SciOMYZin®. 

kk. Subcosta absent or vestigial, or if present, then 
apparently ending in the costa at the point where 
Ri joins it; Ri usually ends in the costa at or before 
the middle of the wing. 

I . Arista long plumose, or pectinate above; oral vibris¬ 

sae present; anal cell complete; costa broken at 
the apex of Ri. Drosophila, Phortica, and other 
genera. Drosophilid® 

II . With another combination of characters. 

m. The cell M and first M2 not separated by a cross¬ 
vein; anal cell absent; front bare or only 







Diptera 


297 


bristly above; usually light colored flies. 
Hippelates, Oscinus, and other genera. (See 

also mmm . Oscinid® 

mm. Cell M and cell first M2 often separated by a 
crossvein; aijal cell present, complete, though 
frequently small; scutellum without spines 
or protuberances; oral vibrissae present; 
arista bare or short plumose; front bristly at 
vertex only; small dark flies. Piophila 
(fig. 99), Sepsis and other genera. . . SEPSID® 
mmm. The Geomyzid®, Agromyzid®, Psilid®, 
Trypetid®, Rhopalomerid®, Borborid® 
and Diopsid® differ in various particulars 
from either the OSCINID® and the SEPSID® 
noted above. 

jj. Squamae well developed, usually large, the lower one 
frequently projecting from below the upper one; both 
posthumeral and intraalar macrochaetae present; 
thorax with a complete transverse suture; postalar 
callus present and separated by a distinct suture from 
the dorsum of the thorax; front of the female broad, 
of the male frequently narrow, the eyes then nearly or 
quite contiguous; the connectiva adjoining the ventral 
sclerites either visible or not; hypopleural macro¬ 
chaetae present or absent; subcosta always distinct in 

its whole course, Ri never short. 

.Calyptrate Muscoidea* 

k. Oral opening small, mouth parts usually much reduced 
or vestigial. This family is undoubtedly of poly- 
phyletic origin but for convenience it is here con¬ 
sidered as a single family. Oestrid® . 

1 . The costal vein ends at the tip of R-4+5, Mi+ 2 
straight, not reaching the wing margin, hence 
cell R5 wide open (fig. i63j); squamae small; 
arista bare; ovipositor of the female elongate. 
Larvae in the alimentary canal of horses, etc. 

. Gastrophilus 

m. Posterior crossvein (m-cu) wanting; wings 
smoky or with clouds. Europe. G. pecorum 
mm. Posterior crossvein (m-cu) present, at least in 
part. 

*The classification of the Muscoidea as set forth by Schiner and other earlier writers has 
long been followed, although it is not satisfactory, being admittedly more or less artificial. With¬ 
in the last two or three decades several schemes have been advanced, that of Braaer and Bergen- 
stamm and of Girschner, with the modifications of Schnabl and Dziedzicki having obtained most 
favor in Europe. Townsend, in jqoS, proposed a system which differs from Girschner’s in some 
respects, but unfortunately it has not yet been published in sufficient detail to permit us to adopt 
it. From considerations of expediency we use here the arrangement given in Aldrich's Cata¬ 
logue of North American Diptera, though we have drawn very freely upon Girschner's most excel¬ 
lent paper for taxonomic characters to separate the various groups. 

It may sometimes be found that a species does not agree in all the characters with the synop¬ 
sis; in this case it must be placed in the group with which it has the most characters in common. 








298 


Hominoxious A rth ropods 


n. Wing hyaline with smoky median cross band, 
and two or three spots; posterior trochanters 
with hook in the male and a prominence in 
the female. World wide distribution. G. equi. 
nn. Wings without spots. 

o. Posterior crossvein (m-cu) distad of the 
anterior crossvein (r-m); legs, particularly 
the femora, blackish brown. Europe and 

North America . G. haemorrhoidalis 

00. Posterior crossvein opposite or proximad of 
the anterior crossvein. Europe and North 

America . G. nasalis 

11 . The costal vein ends at the tip of Mi 2, M1+2 with a 
bend, the cell R5 hence much narrowed in the 
margin, or closed. 

m. Proboscis geniculate, inserted in a deep slit; 
female without extricate ovipositor; arista 
either bare or plumose; squamae large; facial 
grooves approximated below, 

n. Arista bare, short. Larvae in rodents. Tropic 

America. B. princeps . Bogeria Austen 

nn. Arista pectinate above. 

o. Tarsi broadened and flattened, hairy, anal 
lobe of the wing large. Larvae in rodents. 
A number of American species. Cuterebra. 
00. Tarsi slender, not hairy; anal lobe of the 
wing moderate. Larvae in man and other 
mammals. Tropic America. D.cyaniven- 

tris.Dermatobia Br. 

mm. Mouth parts very small, vestigial; arista bare, 
n. Facial grooves approximated below, leaving a 
narrow median depression or groove, 
o. Cell R5 closed and petiolate, body nearly 
bare. Larvae in the nasal cavities of the 
smaller Ungulates. The sheep bot fly. 
O. ovis. Widely distributed. Oestrus L. 
00. Cell R5 narrowly open, body hairy. Larvae 
parasitic on deer. Europe and America 

. Ceplienomyia Latr. 

nn. Facial grooves far apart, enclosing between 
them a broad shield-shaped surface; squamae 
large; female with elongate ovipositor. 

Larvae hypodermatic on Ungulates. 

. Hypoderma Clark 

o. Palpi wanting; tibiae thickened in the middle, 

p. Hair at apex of the abdomen yellow; legs 
including femora yellowish brown.... 

H. diana 










Dipt era 


299 


pp. Hair at the apex of the abdomen reddish 
yellow. Europe and America, 
q. Tibiae and tarsi yellow; femora black 

. H. lineata 

qq. Legs black with black hair; tips of 
hind tibia and tarsi yellowish brown 

. H. bovis 

00. Palpi small, globular; tibiae cylindrical, 

straight. On reindeer. O. tarandi 

. Oedemagena Latr. 

kk. Oral opening of the usual size; mouth parts not 
vestigial. 

1 . Hvpopleurals wanting; if three sternopleurals are 
present the arrangement is 1:2; conjunctiva 
(fig. 161 c) of the venter usually present; if the 
terminal section of M1+2 is bent it has neither fold 
nor appendage (AnthomyiiDjE of Girschner). 

m. Sternopleurals wanting; M1+2 straight toward 
the apex, costa ends at or slightly beyond the 

tip of R4+5; mouth parts vestigial . 

. GASTR0PHILIN>E. See OESTRIDiE 

mm. Sternopleurals present, if rarely absent then 
differing in other characters, 

n. Caudal margin of the fifth ventral abdominal 
sclerite of the male deeply notched on the 
median line usually to beyond the middle; 
abdomen often cylindrical or linear; abdomen 
often with four to eight spots; eyes of the 
male usually widely separated; stemo- 
pleurals three, arranged in an equilateral 
triangle; subapical seta of the hind tibia 
placed very low; M1+2 straight; anal vein 
abbreviated; wings not rilled. Ccenosia, 
Caricea, Dexiopsis, Hoplogaster, Schceno- 

myia, etc. (Ccenosin/e)* . 

. Anthomyiid.-e in part 

nn. Caudal margin of the fifth ventral abdominal 
sclerite of the male incurved, rarely deeply 
cleft, rarely entire, in a few' genera 
deeply two or three notched; M1+2 straight 

♦There are several genera of flies of the family Cordylurida (i.e. Acalyptratce ) which might be 
placed with the Anlhomyiida (i.e. Calyptrala ), owing to the relatively large size of their squamae. 
As there is no single character which will satisfactorily separate all doubtful genera of these two 
groups we must arbitrarily fix the limits. In general those forms on the border line having a 
costal spine, or lower squama larger than the upper, or the lower surface of the scutellum more 
or less pubescent, or the eyes of the male nearly or quite contiguous, or the eyes hairy, or the 
frontal setae decussate in the female; or any combination of these characters may at once be 
placed with the Anthomyiida. Those forms which lack these characteristics and have at least 
six abdominal segments (the first and second segments usually being more or less coalescent) 
are placed with the Acalyptrates. There are other acalyptrates with squamae of moderate size 
which have either no vibrissae, or have the subcosta either wholly lacking or coalescent in large 
part with R,, or have spotted wings; they, therefore will not be confused with the calyptrates. 










3 °° 


Hominoxious Arthropods 


or curved; abdomen usually short or elongate 
oval; sternopleurals, if three are present, 
arranged in the order 1:2 ina right triangle. 
.... (MusciNjE-Anthomyiin.® of Girschner) 

o. M]-j-2 straight, hence cell R5 not narrowed in 

the margin . AnthomytiDjE in part 

p. Underside of the scutellum more or less 
sparsely covered with fine hairs; anal 
vein nearly ahvays reaches the hind 
margin of the wing; extensor surface of 
the hind tibiae with a number of stout 
setae; squamae often small and equal. 
Anthomyia, Chortophila, Eustalomyia, 
Hammomyia, Hylemyia, Prosalpia, Pego- 
myia, etc. . . . HylemyiNjE-Pegomyin.® 
pp. Underside of the scutellum bare; anal 
vein does not reach the wing margin, 

q. First anal vein short, second anal sud¬ 
denly flexed upwards; hind tibiae each 
with one or two strong setae on the 
extensor surface. Fannia ( = Homalo- 
myia), Ccelomyia, Choristoma, Eur- 
yomma, Azelia, etc. FANNIN.E-AZELIN.E 
qq. Anal veins parallel or divergent. 

r. Setae on the exterior surface of the hind 
tibiae wanting (except in Limnaricia 
and Ccenosites), lower squama not 
broadened to the margin of the 
scutellum. Leucomelina, Limno- 
phora, Limnospila, Lispa, Mydaea, 

Spilogaster, etc. 

. MYD.EIN/E-LIMNOPHORIN.E 

rr. One (rarely more) seta on the extensor 
surface of the hind tibia; squamae 
usually large and unequal. Hydro- 
taea, Aricia, Drymeia, Ophyra, 
Phaonia (= Hyetodesia ), Pogono- 
myia, Trichophthicus, etc. Aricine 
00. M1+2 curved or bent, hence the cell R5 more 
or less narrowed in the margin. 
(MusciNiE). MusciDiE in part. See 
page 303 for generic synopsis. 

11 . Hypopleurals present; when three sternopleurals 
are present the arrangement is 2:1 or 1 : 1 : 1 . 

. (Tachinid^e of Girschner) 

m. Conjunctiva of the ventral sclerites of the ab¬ 
domen present, frequently well developed, 
surrounding the sclerites. 






Diptera 


3 QI 


n. Mouth parts vestigial. Oestrid^e. See page 
297 for generic synopsis, 
nn. Mouth parts well developed. 

o. M1+2 straight, hence cell R& wide open in 
the margin; costa ending at the tip of R5; 
three stemopleurals present; antennal 
arista plumose. Syllegoptera. Europe. 
.... (Syllegopteriis) . . Dexiid.e in part 
00. M1+2 bent, hence cell R5 narrowed in the 
margin; stemopleurals rarely wanting, 
usually 1 :i or 0:1; facial plate strongly 
produced below vibrissal angle like the 
bridge of the nose; antennal arista bare. 
Parasitic on Hemiptera and Coleoptera. 
Allophora, Cistogaster, Clytia, Pliasia, 
etc. (Phasiin/e) . .Tachinid^e in part, 
mm. Conjunctiva of the ventral sclerites invisible 
(fig. 161a). 

n. Second ventral sclerite of the abdomen lying 
with its edges either upon or in contact with 
the ventral edges of the corresponding 
dorsal sclerite. 

o. Outermost posthumeral almost always lower 
(more ventrad) in position than the pre- 
sutural macrochaeta; fifth ventral abdomi¬ 
nal sclerite of the male cleft beyond the 
middle, often strongly developed; body 
color very frequently metallic green or 
blue, or yellow; arista plumose. (CALLI- 

phorin.*).MusciDjE in part. 

See page 303 for generic synopsis. 

00. Outermost posthumeral macrochaeta on 
level or higher (more dorsad) than the 
presutural macrochaeta; arista bare, pube¬ 
scent, or plumose only on the basal two- 
thirds; body coloring usually grayish 

(fig. 106) . SARCOPHAGIDiE 

p. Fifth ventral sclerite of the male either 
wanting or with the caudal margin 
straight; presutural intraalar rarely 

present . (Sarcophagus) 

q. Fifth ventral abdominal sclerite of the 
male much reduced, the remaining 
segments with straight posterior mar¬ 
gin, overlapping scale-like; in the 
female only segment one and two scale¬ 
like, the others wholly or in part 
covered; stemopleurals usually three 
or more. Sarcophaga and related 
genera. 





302 


Hominoxious Arthropods 


qq. Fifth ventral sclerite of the male plainly 
visible; sternopleurals usually two. 
Sarcophila, Wohlfahrtia, Brachycoma, 
Hilarella, Millogramma, Metopia, 
Macronychia,, Nyctia, Paramacrony- 
chia, Pachyphthalmus, etc. 
pp. Fifth ventral abdominal sclerite of the 
male cleft to beyond the middle; ventral 
sclerites usually visible, shield-like. 
Rhinophora, Phyto, Melanophora. . . . 
. Rhinophorin/e 



164. Glossina palpalis. (X 4 .) After Austen. 


nn. Second ventral abdominal sclerite as well as 
the others more or less covered, sometimes 
wholly, by the edges of the dorsal sclerite. 
o. The presutural intraalar wanting; ventral 
sclerites two to five nearly or quite covered 
by the edges of the corresponding dorsal 
sclerites; base of the antenna) usually at or 
below the middle of the eye; arista usually 
plumose; legs usually elongate; abdomi¬ 
nal segments with marginal and often 

discal macrocha;tae. Dexiidaj 

00. Presutural intraalar present, if absent, then 
the ventral sclerites broadly exposed 
or the fifth ventral sclerite vestigial; 









Muscidaz 


303 


base of the antennae usually above the 
middle of the eye; arista bare; at least 
two posthumerals and three posterior 
intraalars present. Parasitic on cater¬ 
pillars, etc. Tachinid^e 

SYNOPSIS OF THE PRINCIPAL GENERA OF THE MUSCID.® OF THE WORLD 

. Proboscis long, directed forward, adapted for piercing, or oral margin much 
produced, snout-like. 

b. Oral margin produced snout-like; vibrissa placed high above the oral 
margin; antennal arista either pectinate or more or less plumose, 

c. Antennal arista short or long-plumose; neither sex with distinct 


orbital bristles. 

d. No facial carina between the antennae . Rhynchomyiin.e 

e. Arista short-plumose. R.speciosa. Europe .... Rhynchomyia R. D. 
ee. Arista long-plumose. I. phasina. Europe and Egypt. Idiopsis. B.B. 
dd. With flattened carina, the bases of the antennae separated; no abdom¬ 
inal macrochaetae . Cosminin^e 

C. fuscipennis. South Africa . Cosmina 

cc. Antennal arista pectinate; bases of the antennae separated by a flat¬ 
tened carina . Rhiniinve R. D. 

d. Cell R5 open, or closed at the margin. 


e. Third segment of the antenna twice as long as the second; claws of 
both sexes short; cell R5 open. I. lunata. Eastern Hemisphere. 

. Idia Meigen 

ee. Third segment of the antenna three times as long as the second; 
cell R5 open or closed; claws of the male long and slender, of the 
female shorter than the last tarsal joint. I. mandarina, China. 

. Idiella B. B. 

dd. Cell R5 petiolate. Rhinia; and Beccarimyia Rdi. 

bb. Proboscis long, directed forward, adapted for piercing. STOMOXIN^E 

c. Arista flat, pectinate above with plumose rays; sternopleurals 1:2; 
bases of the veins Ri and R4+5 without setae; base of the media bowed 
down; apical cell opens before the apex of the wing. African species 

. Glossina Wied. 

d. Species measuring overtw r elve mm. in length. G. longipennis and fusca. 
dd. Species less than twelve mm. in length, 

e. All segments of the hind tarsi black. 

f. The fourth and fifth segments of the fore tarsi black; antennae 

black (fig. 164) . G. palpalis R. D. 

ff. Otherwise marked. G. bocagei, tachinoides, pallicera. 

ee. First three segments of the hind tarsi are yellow, the fourth and 
fifth segments are black. 

f. Fourth and fifth segments of the first and second pair of tarsi are 
black. 

g. The yellow bands of the abdominal segments occupy a third of 

the segment (fig. 165). G. morsitans Westw. 

gg. The yellow band on each segment of the abdomen occupies a 
sixth of the segment. G. longipalpis Wied. 
















304 Hominoxious Arthropods 

ff. Tarsi of the first and second pairs of legs wholly yellow. 

. G. pallidipes Austen 

cc. Rays of the arista not plumose; only one or two stemopleurals; base of 
the media not strongly bowed down; apical cell opens at or very near 
the apex of the wing. 

d. Vein R4+5 without setae at the base; palpi about as long as the pro¬ 
boscis. 

e. Arista pectinate (i. e. rays on one side only), the rays often undulate; 
two yellow stemopleurals often difficult to detect; vein M 1-1-2 
only slightly bent, the apical cell hence wide open. The horn fly, 
H. irritans ( = Lyperosia serrata) and related species. Widely dis¬ 
tributed (figs. 167, 168).Haematobia R. D. not B. B. 



165. Glossina morsitans. (X 4 .) After Austen. 


ee. Arista also with rays below; vein M1+2 more strongly bent, the 
apical cell hence less widely open. 

f. Palpi strongly spatulate at the tips, lower rays of the arista about 

six in number, B. sanguinolentus. South Asia. 

. Bdellolarynx Austen 

ff. Palpi feebly spatulate; apical cell of the wing narrowly open 
slightly before the tip; stemopleurals black, anterior bristle 

sometimes absent. H. atripalpis. Europe. 

. Haematobosca Bezzi 


dd. Vein R4A5 with setae at the base.* 


*Pachymyia Macq. is closely related to Stomoxys. It differs in having the arista rayed both 
above and below. P. vexans, Brazil. 



















Muse idee 


305 


e. Veins Ri and R.j-j-5 with setae at the base; two equally prominent 
stemopleural macrochaetae; arista with rays both above and be¬ 
low; palpi as long as the proboscis; apical cell of the wing wide 

open. L. tibialis. ( Hcematobia B. B. not R. D.) . 

. Lyperosiops Town. 

ee. Only vein R4+5 with basal setae; anterior stemopleural macro- 
chaeta wanting; arista pectinate. 

f. Palpi as long as the proboscis, the latter stout, with fleshy termi¬ 
nal labellae; apical cell narrowly open; stemopleural macro¬ 
chaetae black. S. maculosa from Africa and related species 

from Asia. Stygeromyia Austen 

ff. Palpi much shorter than the proboscis, the latter pointed at the 
apex, without fleshy labellae; apical cell of the wing wide open. 
S. calcitrans, the stable fly and related species. Widely dis¬ 
tributed in both hemispheres (fig. no). Stomoxys Geof. 

aa. Proboscis neither slender nor elongate, the labellae fleshy and not adapted for 
piercing. 

b. Hypopleurae without a vertical row of macrochaetae.MUSCIN^E 

c. Arista bare; distal portion of R4+5 broadly curved at the end; hypop- 
pleurae with a sparse cluster of fine hairs. S. braziliana, Southern 

States and southward . Synthesiomyia B. B. 

cc. Arista pectinate or plumose. 

d. Arista pectinate. H. vittigera, with the posterior half of the abdomen 

metallic blue. Mexico. Hemichlora V. d. W. 

dd. Arista plumose. 

e. Middle tibia with one or more prominent setae on the inner (flexor) 
surface beyond the middle, or inner surface very hairy, 

f. Ri ends distad of the m-cu crossvein; R4+5 with a broad curve 
near its apical end. (= Neomesembrina Schnabl, = Metamesem- 
brina Town). M. meridiana. Europe. . . . Mesembrina Meigen 
ff. Ri ends proximad of the m-cu crossvein. 

g. Eyes pilose, sometimes sparsely in the female. 

h. Female with two or three stout orbital setae; the hind metatar¬ 
sus of the male thickened below 7 at the base and penicillate. 

D. pratorum. Europe. Dasyphora R. D.* 

hh. Neither sex with orbital setae. 

i. Abdomen without macrochaetae; arista plumose. C. 

asiatica. Eastern Hemisphere... Cryptolucilia B. B. 

ii. Abdomen with strong macrochaetae; arista very short- 

plumose, nearly bare. B. tachinina. Brazil . 

. Reinwardlia B. B. 

gg. Eyes bare. 

h. Body densely pilose; thoracic macrochaetae wanting; middle 
tibiae much elongate and bent; last section of R4+5 with a 
gentle curve. H. ( Mesembrina ) mystacea, el al., Europe 
and H. solilaria, N. America . . . Hypodermodes Town, 
hh. Body not densely pilose. 


♦The genus Eudasyphora Town, has recently been erected to contain D. lasiophthalma. 













3°6 


Hominoxious Arthropods 


i. Dorsocentrals six; last section of R4+5 with a gentle curve, 
j. Inner dorsocentrals (“acrostichals”) wanting; sterno- 

pleurals arranged 1:3. P. cyanicolor, cadaverina, etc. 

Europe and America. Pyrellia R. D. 

jj. Inner dorsocentrals (“acrostichals”) present; stemo- 
pleurals arranged 1:2. E. latreillii. North America. 
. Eumesembrina Town. 

ii. Dorsocentrals five; inner dorsocentrals present; last 

section of R4+5 with a rounded angle; stemopleurals 
arranged 1:2. P. cornicina Europe and America. 

{Pseudopyrellia Girsch.). Orthellia R. D. 

ee. Middle tibia without a prominent bristle on the inner surface beyond 
the middle. 



166. Pycnosoma marginale. (X4.) After Graham-Smith. 


f. Squamula thoracalis broadened mesad and caudad as far as the 
scutellum. 

g. Stemopleural macrochsetae arranged in an equilateral triangle; 
front of both sexes broad; gense bare; dorsocentrals six, 
small; wing not rilled. (To Coenosin.®). Atherigona Rdi. 
gg. Stemopleural macrochaetae when three are present, arranged 
in a right triangle. 

h. Last section of R44-5 with a more or less rounded angle 
(fig. 163I). 

i. Eyes of the male pilose or pubescent, of the female nearly 

bare; m-cu crossvein usually at or proximad of the mid¬ 
distance between the r-m crossvein and the bend of 

R4+5. P. (= Placomyia R. D.) vitripennis . 

.. Plaxemyia R. D. 

ii. Eyes bare; the m-cu crossvein always nearer to the bend of 

R4-I-5 than to the r-m crossvein, 

j. Apex of the proboscis when extended reveals a circlet of 
stout chitinous teeth. P. insignis Austen, of India, 
bites both man and animals. (= Pristirhynchomyia) 
. Philaematomyia Austen 








Muscidaz 


3°7 


jj. Apex of the proboscis without black teeth. 

k. Eyes of male separated by a distance equal to a fourth 
the width of the head. House or typhoid fly. 
M. domestica L. Widely distributed.. Musca L. 
kk. Eyes of the male contiguous. E. corvina. Europe. 

.Eumusca Town 

hh. Last section of R4+5 with a gentle curve (fig. 102). 

i. Eyes pilose. 

j. Claws in the male somewhat elongated; no orbitals in 
either sex; antennas separated at the base by a flat 
carina; abdomen marked with red or yellow. G. 
maculata. Europe and America... .Graphomyia R. D. 
jj. Claws short and equal in the two sexes; two or three 
stout orbital macrochaetae in the female; Rj scarcely 
produced beyond the r-m crossvein; eyes contiguous 
in the male. P. obsoleta. Brazil . . Phasiophana Br. 

ii. Eyes bare; fronto-orbital macrochaetae in a double row, 

antennae contiguous at the base, 
j. One or more pairs of well developed anterior inner dorso- 
central (acrostichal) macrochaetae; seta on extensor 
surface of hind tibia. M. assimilis, stabulans, etc. 

Europe and America.Muscina R. D. 

jj. Anterior inner dorsocentrals and the setae on the ex¬ 
tensor surface of the hind tibia wanting. M. micans, 
etc. Europe and North America. . . .Morellia R. D. 
ff. Squamula thoracalis not broadened mesad and caudad, not 
reaching the margin of the scutellum; macrochaetae on extensor 
surface of the hind tibia wanting, 
g. Eyes pubescent. M. meditabunda. Europe and America. 

. Myiospila Rdi. 

gg. Eyes bare; Ri ends before the middle of the wing. A number 

of species from the tropics of both hemispheres. 

. Clinopera V. d. W. 

bb. Hypopleurae with a vertical row of macrochaetae. 

c. Eyes pubescent. 

d. Rj ends about opposite the r-m crossvein; basal section of R4+5 bristly 
nearly to the crossvein; S. enigmatica. Africa. Somalia Hough 
dd. Ri ends distad of the r-m crossvein. 

e. Eastern hemisphere. Australasia. N. ochracea, dasypthalma. 

. Neocalliphora Br. 

ee. Western Hemisphere. T. muscinum. Mexico. . Tyreomma V. d. W. 
cc. Eyes bare. 

d. The vibrissal angle situated at a noticeable distance above the level of 
the margin of the mouth. 

e. Sternopleural macrochaetae arranged in the order 1:1. 

f. Genae with microchaetae. 

g. Body grayish, with depressed yellow woolly hair among the 
macrochaetae; wings folded longitudinally over the body when 








3°8 


Hominoxious Arthropods 


at rest. Cluster flies. P. rudis and related species, widely 

distributed . Pollenia R. D.* 

gg. Body metallic blue or green. Eastern Hemisphere. 

h. Vibrissal angle placed very high above the oral margin; a 
carina between the antenna*; outer posthumeral wanting; 

anterior intraalar present. T. viridaurea. Java . 

. Thelychceta Br. 



167. Horn fly. (a) egg; (2>) larva; (c) puparium; ( d ) adult. (X4). Bureau of Entomology 

hh. Vibrissal angle moderately high above the oral margin; 
carina small or wanting; no post humeral macrochaeta; 
lower squama hairy above. ( = Paracompsomyia 

Hough) (fig. 166) . Pycnosoma Br. 

ff. Gena bare. S. terminata. Eastern Hemisphere . 

. Strongyloneura Bigot 

ee. Stemopleurals arranged 2:1. 

f. Body metallic green or blue, with gray stripes; gena hairy to the 
lower margin; post humerals often wanting; lower squama bare 

above. ( = Compsomyia Rdi.) . Chrysomyia R. D. 

g. With one or two orbitals; height of bucca less than half the 

height of the eye. South and east U. S. (fig. 107) . 

. C. marcellaria 

gg. No orbitals; height of bucca about a third less than height of 
eye. West U. S . C. wheeler i Hough 

*Nitellia, usually included in this genus has the apical cell petiolate. A pollenia Bezzi, has 
recently been separated from Pollenia to contain the species P. nudiuscula. Both genera belong 
to the Eastern hemisphere. 



























Muscidce 


3°9 


ff. Body black or sordidly metallic greenish gray, usually yellow pol- 
linose or variegate; genae at most hairy above. N. slygia. 

Eastern Hemisphere. Neopollenia Br. 

dd. Vibrissal angle situated nearly on a level of the oral margin, 

e. Species wholly blackish, bluish, or greenish metallic in color. 

f. First section of R4+5 with at most three or four small bristles at 
the immediate base. 

g. The bend of R4+5 a gentle curve; costal spine present; cell R5 
closed, ending before the apex of the wing. 5 . cuprina. 

Java. Synamphoneura Bigot 

gg. Bend of R4+5 angular; or the insect differs in other characters ; 
dorsal surface of the squamula thoracalis hairy (except in 
Melinda)-, arista plumose only on the basal two-thirds 
(except usually in Calliphora and Eucalliphora). 



1G8. Head of horn-fly (Lyperosia irritans); (a) female; (6) male; (c) lateral aspect of female. 

h. Arista plumose only on the basal two-thirds. 

i. Base of the antennae ventrad of the middle of the eye; eyes 
of the male nearly contiguous; genae hairy; second 
abdominal segment with median marginal macrochaetae; 
two, rarely three, postsutural intraalar macrochaetae. 

j. Squamula thoracalis dorsally with long black hairs; male 
hypopgium two-segmented, large, projecting; claws 
and pullvilli of the male elongate; three strong stemo- 
pleural macrochaetae; genae at least half the width of the 
eye; buccae (cheeks) half the height of the eyes; ovivi- 

parous. 0 . sepulcralis. Europe . Onesia R. D. 

jj. Dorsal surface of the squamula thoracalis bare; male 
hypopygium small, scarcely projecting below; claws 
and pulvilli not elongate; two stout stemopleural 
macrochaetae, sometimes with a delicate one below the 
anterior; genae nearly linear in the male ; buccae about 
a third of the eye height; oviparous. M. ccerulea. 
Europe. Melinda. R. D. 









3 IO 


Hominoxious Arthropods 



169. Lateral and dorsal aspects of the thorax, and frontal aspect of the head of a muscoidean 
fly, with designations of the parts commonly used in taxonomic work. 

























Muscidce 


3ii 

ii. Base of the antennae dorsad of the middle of the eye; eyes 
of both sexes distinctly separated; dorsal surface of 
the squamula thoracalis with black hairs; two post 
sutural intraalar macrochaetae. 
j. Hypopygium of the male large, with a pair of slightly 
curved forceps whose ends are concealed in a longi¬ 
tudinal slit in the fifth ventral sclerite; third posterior 
inner dorso-central (acrostichal) macrochaetae absent; 
anterior intraalar rarely present; abdomen usually not 
pollinose; the second segment without median marginal 
macrochaetae; face yellow. C. mortuorum, cadaverina, 
and related species. Both hemispheres. 



170. Sepsis violacea; puparium and adult. (See page 297 .) After Howard. 


jj. Three pairs of posterior inner dorsocentrals (acrostichals) 
present; second abdominal segment with a row of 
marginal macrochaetae; genae hairy, at least above, 
k. Hypopygium of the male with a projecting style. 
5 . stylifera. Europe. Steringomyia Pok. 


*The following three genera are not sufficiently well defined to place in this synopsis. In 
color and structural characters they are closely related to Cynomyia from which they may be 
distinguished as follows. Calapicephala Macq., represented by the species C. splendens from 
Java, has the setae on the facial ridges rising to the base of the antennae and has median margi¬ 
nal macrochaetae on the abdominal segments two to four: Blepharicnema Macq., represented by 
B. splendens from Venezuela has bare genae, oral setae not ascending; tibiae villose; claws short 
in both seses; Sar'onesia Bigot with the species -S', chlorogaster from Chile, setose genae; legs 
slender, not villose; claws of the mae! elongate. 






312 


Hominoxious A r thro pods 


kk. Hypopygium of the male without style. A. stelviana 

B. B . Acrophaga B. B. 

hh. Arista usually plumose nearly to the tip; posterior dorso- 
centrals and inner dorsocentrals (acrostichals) well 
developed; dorsal surface of the squamula thoracalis 
hairy; abdomen metallic and usually pollinose; genae 
hairy. 

i. With one pair of ocellar macrochaetae. C. vomitoria, 

erythrocephala, viridescens, and related species. Both 
hemispheres . Calliphora R. D. 

ii. With two strong pairs of ocellar macrochaetae. .E. latifrons. 

Pacific slope of the U. S . Eucalliphora Town. 

ff. First section of R4+5 bristly near or quite half way to the small 
crossvein; dorsal surface of the squamula thoracalis is bare; 
the hypopygium of the male is inconspicuous, 

g. Genae bare; posterior inner and outer dorsocentrals distinct 
and well developed. L. ccesar, sericata, sylvarum, and 
related species. Widely distributed in both hemispheres 

(fig. 103).Lucilia R. D. 

gg. Genae with microchaetae, at least down to the level of the base 
of the arista. 

h. Mesonotum flattened behind the transverse suture. 

i. Posterior dorsocentrals inconstant and unequally developed; 

one pair of posterior inner dorsocentrals. P. terraenova. 
North America. Protophormia Town. 

ii. Posterior dorsocentrals well developed, the inner dorso¬ 

centrals (acrostichals) unequally developed. P. azurea, 

chrysorrhcea, etc. Europe and America . 

. Protocalliphora Hough 

hh. Mesonotum not flattened behind the transverse suture; 
posterior inner and outer dorsocentrals inconstant 
and unequally developed. P. regina. Europe and 

America . Phormia R. D. 

ee. Species more or less rufous or yellow in color. 

f. Anterior dorsocentrals wanting; first section of the R4+5 at most 
only bristly at the base, bend near apex rectangular, Ri ends over 
the crossvein; fronto-orbital macrochaeta absent; eyes of the 
male contiguous. C. semiviridis. Mexico . . Chloroprocta V. d. W 
ff. With another combination of characters. 

g. Body robust, of large size, abdomen elongate, not round; genae 
with several ranges of microchaetae; vibrissal ridges strongly 
convergent; abdomen with well developed macrochaetae; 
costal spine usually absent; eyes of the male widely separated, 

h. Peristome broad, pteropleural macrochaetae distinct; one or 
two sternopleurals; in the female a single orbital macro¬ 
chaeta; last abdominal segment without discal macro¬ 
chaetae; hypopygial processes of the male with a long 
stylet; second abdominal segment of the female sometimes 










171. Stigmata of the larvae of Muscoidea. Third instar. (a) Cynomyia cadavarina; ( 6 ) Phormia regina; (c) Chrysomyia macel- 
laria; (d) Musca domestica; (e) Sarcophaga sp ; (/) Oestris ovis; ( g ) Gastrophilus equi; ( h) Sarcophaga sp; (»') Pegomyia 
vicina; (j) Protocalliphora azurea; (k) Hypoderma lineata; ( l ) Muscina stabulans. Magnification for f, g, and k. x 25 ; 
all others, x 50 . 


Muscidos 


313 





3i4 


Hominoxious Arthropods 


much elongate. A. luteola (fig. 86). Africa. The sub¬ 
genus Cheeromyia Roub. is included here. Auchmeromyia B.B. 
hh. Peristome narrow; no pteropleurals, two sternopleurals; 
two orbitals in the female; second segment not elongate; 
the fourth with two well developed discal macrochaetae. 

B. depressa. Africa.Bengalia R. D 

gg. With another combination of characters. 

h. Costal spine present; body in part black; antennas notice¬ 
ably shorter than the epistome, inserted above the middle 
of the eye and separated from each other by a carina; 
abdominal segments with marginal macrochaetas; stemo- 

pleurals 2:1 or 1:1. Paratricyclea Villen. 

hh. Costal spine not distinct, or if present, insect otherwise 
different. 

i. Genae with several ranges of microchaetae; vibrissal ridges 

strongly converging; peristome broad; arista moderately 
plumose; sternopleurals usually 1:1; color entirely 

testaceous. C. anthropophaga (fig. 87) and grunbergi. 

Africa.Cordylobia Grunb. 

ii. Genae bare or with but one range of setae; vibrissal ridges 

less converging; peristome narrow; arista long plumose, 

j. Genas with a single row of microchaetae. 

k. Sternopleurals 2:1; color entirely testaceous. 

. Ochromyia Macq. * 

kk. Sternopleurals l:l. P. varia Hough. Africa. 

. Parochromyia Hough 

jj. Genae bare. 

k. Basal section of R4+5 bristly only at the immediate 
base, distal section with a broad curve; distal 

portion of the abdomen metallic; sternopleurals 

usually 1:1. rarely 2:1. M. ceneiventris Wd. Tropic 

America. Mesembrinella. G. T. 

kk. R4+5 bristly at least nearly half way to the small 
crossvein; sternopleurals 1:1. 

I . Macrochaetas of the abdomen marginal; neither sex 

with orbitals; no carina between the base of the 
antennae; three pairs of presutural inner dorso- 
centrals. Eastern hemisphere. T. ferruginea. 
Tricyclea V. d. W. ( = Zonochroa B. B. according 
to Villeneuve 1914). 

II . Abdomen without macrochaetas; wing usually with 

a marginal streak and gray markings. Brazil 
. Hemilucilia B. B. 


*Plinlhomyia Rdi. and Hemigymnochiita Corti are related to Ocliromyia, though too briefly 
described to place in the key. 












Muscoidea 


3i5 



median line is indicated in each figure. 













Si6 


Homi-noxious Arthropods 


SIPHONAPTERA. Fleas 
Adapted from a table published by Oudemans. 

a. Elongated fleas, with jointed (articulated) head, with combs (ctenidia) on 
head and thorax; with long, oval, free-jointed flagellum of the antenna 

(fig. 92d).Suborder FRACTICIPATA 

b. With ctenidia in front of the antennae and on the genae (cheeks); maxillae 
with acute apices; labial palpi five-segmented, symmetrical; eyes poorly 

developed or wanting. On rodents. Hystrichopsyllid.e 

c. Abdominal segments without ctenidia. 

d. Post-tibial spines in pairs and not in a very close set row; head with 

ctenidia. Ctenophthalmus Kol. 

dd. Post-tibial spines mostly single and in a close set row. Ctenopsyllus 
and Leptopsyllus. The last genus has recently been erected for 
L. musculi, a widely distributed species occurring on rats and mice, 
cc. Abdominal segments with one or more ctenidia; post-tibial spines in 
numerous, short, close-set transverse rows on posterior border with 
about four spines in each row. H. americana. . Hystrichopsylla Taschenb. 
bb. With only two pairs of subfrontal ctenidia; labial palpi five-segmented, 
symmetrical; eyes vestigial or wanting. On bats. ( = Ischnopsyl- 

lid,e) . Nycteridipsyllid.e 

With more or less blunt maxilla; all tibiae with notch; a single antepygi- 
dial bristle; metepimeron without ctenidium. N. crosbyi from 
Missouri was found on bats. Rothschild suggests that this is probably 
the same as N. insignis. 

.( = Ischnopsyllus = Ceratopsyllus), Nycteridiphilus 

aa. Head not jointed, i.e. the segments coalescent, traces of the segmentation 
still being visible in the presence of the vertex tubercle, the falx (sickle¬ 
shaped process), and a suture.Suborder INTEGRICIPITA 

b. Flagellum of the antennas long and oval. 

c. Usually elongate fleas, with a free-segmented flagellum of the antenna; 
thorax not shorter than the head, longer than the first tergite. 

d. Genre of the head and the pronotum with ctenidia. . . . Neopsyllid.e 

e. Labial palpi four or five-segmented; symmetrical; hind coxae with 
patch of spines inside; row of six spatulate spines on each side in 
front of the antennas. C. ornata found on a California mole 

. Corypsylla 

ee. Labial palpi two-segmented, transparent, membranous. On 

hares . Spilopsyllus Baker 

dd. No ctenidium on the head. 

e. Pronotum with ctenidium . Dolichopsyllid^e 

f. Labial palpi five-segmented, symmetrical. 

g. Antepygidial bristles one to three; eyes present. 

h. Inner side of hind coxae distally with a comb of minute teeth; 

falx present. On rodents and carnivores . 

. Odontopsyllus Baker 

hh. Inner side of hind coxae without comb or teeth. Many 

North American species on rodents. 

. Ceratophyllus Curtis 















Siphonaptera 


3 T 7 


gg. Antepygidial bristles five on each side; eyes absent; suture 

white. D. stylosus on rodents. Dolichopsyllus Baker 

ff. Labial palpi four or five-segmented; asymmetrical (membranous 
behind), apex acute. Hoplopsyllus anomalus found on Spermo- 

philes in Colorado . Hoplopsyllid^e 

ee. Pronotum without ctenidium. Anomiopsyllus californicus and 

nudatus on rodents . Anomiopsyllid.e 

cc. Very short fleas; flagellum of the antenna with pseudo-segments coales- 
cent; thorax much shorter than the head and than the first tergite 

. HECTOPSYLLID.E 

Flagellum of the antenna with six coalescent pseudo-segments; maxilla 

blunt. The chigger on man (fig. 93). D. penetrans. 

. (= Rhynchoprion = Sarcopsylla) Dermatophilus Guerin 

bb. Flagellum short, round, free portion of the first segment shaped like a 
mandolin. 

c. Thorax not shorter than the head, longer than the first tergite; flagellum 
either with free segments or in part with the segments coalescent. 

d. Head and pronotum with ctenidium; labial palpi asymmetrical. . . . 

. ARCHjEOPSYLLIDjE 

With four subfrontal, four genal, and one angular ctenidia. Widely 


distributed . Ctenocephalus Kol. 

e. Head rounded in front (fig. 92a). Dog flea . C. canis 

ee. Head long and flat (fig. 92b). Cat flea . C. felis 

dd. Neither head nor pronotum with ctenidium. Labial palpi asym¬ 
metrical, membranous behind . PULICID.® 


e. Mesosternite narrow, without internal rod-like thickening from the 

insertion of the coxae upwards. Human flea, etc.Pulex L. 

ee. Mesosternite broad with a rod-like internal thickening from the 
insertion of the coxae upwards (fig. 89). X. (Loemopsylla) cheopis, 

plague or rat flea. Xenopsylla 

cc. Thorax much shorter than the head and than the first tergite. Echi- 
dnophagidae. E. gallinacea, the hen flea also attacks man (fig. 96). 
.(= Argopsylla =Xestopsylla) Echidnophaga 011 iff_ 
















APPENDIX 


HYDROCYANIC ACID GAS AGAINST HOUSEHOLD INSECTS 

The following directions for fumigating with hydrocyanic acid 
gas are taken from Professor Herrick’s circular published by the 
Cornell Reading Course: 

Hydrocyanic acid gas has been used successfully against house¬ 
hold insects and will probably be used more and more in the future. 
It is particularly effective against bed-bugs, and cockroaches, but 
because it is such a deadly poison it must he used very carefully. 

The gas is generated from the salt potassium cyanid, by treating 
it with sulfuric acid diluted with water. Potassium cyanid is a 
most poisonous substance and the gas emanating from it is also 
deadly to most, if not all, forms of animal life. The greatest care 
must always be exercised in fumigating houses or rooms in buildings 
that are occupied. Before fumigation a house should be vacated. 
It is not necessary to move furniture or belongings except brass or 
nickel objects, which may be somewhat tarnished, and butter, milk, 
and other larder supplies that are likely to absorb gas. If the nickel 
and brass fixtures or objects are carefully covered with blankets 
they will usually be sufficiently protected. 

There may be danger in fumigating one house in a solid row of 
houses if there is a crack in the walls through which the gas may find 
its way. It also follows that the fumigation of one room in a house 
may endanger the occupants of an adjoining room if the walls be¬ 
tween the two rooms are not perfectly tight. It is necessary to keep 
all these points in mind and to do the work deliberately and thought¬ 
fully. The writer has fumigated a large college dormitory of 253 
rooms, once a year for several years, without the slightest accident 
of any kind. In order to fumigate this building about 340 pounds 
of cyanid and the same amount of sulfuric acid were used each time. 
In addition to this, the writer has fumigated single rooms and smaller 
houses with the gas. In one instance the generating jars were too 
small; the liquid boiled over and injured the floors and the rugs. 
Such an accident should be avoided by the use of large jars and by 
placing old mgs or a quantity of newspapers beneath the jars. 


The Proportions of Ingredients 

The Proportions of Ingredients 


3i9 


Experiments and experience have shown that the potassium 
cyanid should be ninety-eight per cent pure in order to give satis¬ 
factory results. The purchaser should insist on the cyanid being of 
at least that purity, and it should be procurable at not more than 
forty cents per pound. The crude form of sulfuric acid may be used. 
It is a thickish, brown liquid and should not cost more than four or 
five cents a pound. If a room is made tight, one ounce of cyanid for 
every one hundred cubic feet of space has been shown to be sufficient. 
It is combined with the acid and water in the following proportions: 


Potassium cyanid. 1 ounce 

Commercial sulfuric acid. 1 fluid ounce 

Water. 3 fluid ounces 


A Single Room as an Example 

Suppose a room to be 12 by 15 by 8 feet. It will contain 
12x15x8, or 1440 cubic feet. For convenience the writer always 
works on the basis of complete hundreds; in this case he would 
work on the basis of 1500 cubic feet, and thus be sure to have enough. 
The foregoing room, then, would require 15 ounces of cyanid, 15 
ounces of sulfuric acid, and 45 ounces of water. The room should 
be made as tight as possible by stopping all the larger openings, 
such as fireplaces and chimney flues, with old rags or blankets. 
Cracks about windows or in other places should be sealed with narrow' 
strips of newspaper well soaked in water. Strips of newspaper two 
or three inches wide that have been thoroughly soaked in water may 
be applied quickly and effectively over the cracks around the window 
sash and elsewhere. Such strips wall stick closely for several hours 
and may be easily removed at the conclusion of the work. 

While the room is being made tight, the ingredients should be 
measured according to the formula already given. The water should 
be measured and poured first into a stone jar for holding at least two 
gallons. The jar should be placed in the middle of the room, with 
an old rug or several newspapers under it in order to protect the floor. 

The required amount of sulfuric acid should then be poured 
rather slowly into the w r ater. This process must never he reversed; 
that is, the acid must never he poured into the jar first. The cyanid 
should be weighed and put into a paper bag beside the jar. All hats, 
coats, or other articles that wall be needed before the work is over 





320 Hydrocyanic Acid Gas Against Household Insects 

should be removed from the room. When everything is ready the 
operator should drop the bag of cyam'd gently into the jar, holding 
his breath, and should walk quickly out of the room. The steam¬ 
like gas does not rise immediately under these conditions, and ample 
time is given for the operator to walk out and shut the door. If 
preferred, however, the paper bag may be suspended by a string 
passing through a screw eye in the ceiling and then through the key¬ 
hole of the door. In this case the bag may be lowered from the out¬ 
side after the operator has left the room and closed the door. 

The writer has most often started the fumigation toward evening 
and left it going all night, opening the doors in the morning. The 
work can be done, however, at any time during the day and should 
extend over a period of five or six hours at least. It is said that bet¬ 
ter results will be obtained in a temperature of 70° F., or above, than 
at a lower degree. 

At the close of the operation the windows and doors may be opened 
from the outside. In the course of two or three hours the gas should 
be dissipated enough to allow a person to enter the room without 
danger. The odor of the gas is like that of peach kernels and is easily 
recognized. The room should not be occupied until the odor has 
disappeared. 

Fumigating a Large House 

The fumigation of a large house is merely a repetition, in each room 
and hall, of the operations already described for a single room. All 
the rooms should be made tight, and the proper quantities of water 
and sulfuric acid should be measured and poured into jars placed 
in each room with the cyanid in bags besides the jars. When all 
is ready, the operator should go to the top floor and work doivnward 
because the gas is lighter than air and tends to rise. 

Precautions 

The cyanid should be broken up into small pieces not larger than 
small eggs. This can best be done on a cement or brick pavement. 
It would be advantageous to wear gloves in order to protect the hands, 
although the writer has broken many pounds of cyanid without any 
protection on the hands. Wash the hands thoroughly at frequent 
intervals in order to remove the cyanid. 

The operations of the work must be carried out according to 
directions. 


Precautions 


321 


The work should be done by a calm, thoughtful and careful 
person—best by one who has had some experience. 

Conspicuous notices of what has been done should be placed on 
the doors, and the doors should be locked so that no one can stray 
into the rooms. 

The gas is lighter than air, therefore one should always begin in the 
rooms at the top of the house and work down. 

After fumigation is over the contents of the jar should be emptied 
into the sewer or some other safe place. The jars should be washed 
thoroughly before they are used again. 

It must be remembered that cyanid is a deadly poison; but it is 
very efficient against household insects, if carefully used, and is not 
particularly dangerous when properly handled. 

LESIONS PRODUCED BY THE BITE OF THE BLACK-FLY 

While this text was in press there came to hand an important paper 
presenting a phase of the subject of black fly injury so different from 
others heretofore given that we deem it expedient to reproduce here 
the author’s summary. The paper was published in The Journal 
of Cutaneous Diseases, for November and December, 1914, under the 
title of “A Clinical, Pathological and Experimental Study of the 
Lesions Produced by the Bite of the Black Fly” ( Simulium venus- 
tum),” by Dr. John Hinchman Stokes, of the University of Michigan. 

Resume and Discussion of Experimental Findings 

The principal positive result of the work has been the experimental 
reproduction of the lesion produced by the black-flv in characteristic 
histological detail by the use of preserved flies. The experimental 
lesions not only reproduced the pathological pictures, but followed 
a clinical course, which in local symptomatology especially, tallied 
closely with that of the bite. This the writer interprets as satis¬ 
factory evidence that the lesion is not produced by any living infec¬ 
tive agent. The experiments performed do not identify the nature 
of the toxic agent. Tentatively they seem to bring out, however, 
the following characteristics. 

1. The product of alcoholic extraction of flies do not contain 
the toxic agent. 

2. The toxic agent is not inactivated by alcohol. 

3. The toxic agent is not destroyed by drying fixed flies. 

4. The toxic agent is not affected by glycerin, but is, if anything, 
more active in pastes made from the ground fly and glycerin, than 
in the ground flies as such. 


322 Lesions Produced by the Bite of the Black-fly 

5. The toxic agent is rendered inactive or destroyed by hydro¬ 
chloric acid in a concentration of 0.25%. 

6. The toxic agent is most abundant in the region of the ana¬ 
tomical structures connected with the biting and salivary apparatus 
(head and thorax). 

7. The toxic agent is not affected by a 0.5 % solution of sodium 
bicarbonate. 

8. The toxic agent is not affected by exposure to dry heat at 
ioo° C. for two hours. 

9. The toxic agent is destroyed or rendered inactive in alkaline 
solution by a typical hydrolytic ferment, pancreatin. 

10. Incomplete experimental evidence suggests that the activity 
of the toxic agent may be heightened by a possible lytic action of 
the blood serum of a sensitive individual, and that the sensitive serum 
itself may contain the toxic agent in solution. 

These results, as far as they go (omitting No. 10), accord with 
Langer’s except on the point of alcoholic solubility and the effect 
of acids. The actual nature of the toxic agent in the black-fly is 
left a matter of speculation. 

The following working theories have suggested themselves to 
the writer. First, the toxin may be, as Langer believes in the case 
of the bee, an alkaloidal base, toxic as such, and neutralized after 
injection by antibodies produced for the occasion by the body. In 
such a case the view that a partial local fixation of the toxin occurs, 
which prevents its immediate diffusion, is acceptable. Through 
chemotactic action, special cells capable of breaking up the toxin 
into harmless elements are attracted to the scene. Their function 
may be, on the other hand, to neutralize directly, not by lysis. 
This would explain the role of the eosinophiles in the black-fly lesion. 
If their activities be essential to the destruction or neutralization 
of the toxin, one would expect them to be most numerous where 
there was least reaction. This would be at the site of a bite in an 
immune individual. A point of special interest for further investiga¬ 
tion, would be the study of such a lesion. 

Second, it is conceivable that the injected saliva of the fly does 
not contain an agent toxic as such. It is possible, that like many 
foreign proteins, it only becomes toxic when broken down. The 
completeness and rapidity of the breaking down depends on the 
number of eosinophiles present. In such a case immunity should 
again be marked by intense eosinophilia. 


173. Fifth day mature lesion. Lower power drawing showing papillary oedema and infiltrate in the region 
of the puncture. 


Lesions Produced by the Bite of the Black-fly 


323 




324 Lesions Produced by the Bite of the Black-fly 

Third, lytic agents in the blood serum may play the chief role 
in the liberation of the toxic agent from its non-toxic combination. 
An immune individual would then be one whose immunity was not 
the positive one of antibody formation, but the negative immunity 
of failure to metabolize. An immune lesion in such a case might 
be conceived as presenting no eosinophilia, since no toxin is liberated. 
If the liberation of the toxin is dependent upon lytic agents present 
in the serum rather than in any cellular elements, a rational explana¬ 
tion would be available for the apparent results (subject to con¬ 
firmation) of the experiment with sensitive and immune sera. In 
this experiment it will be recalled that the sensitive serum seemed to 
bring out the toxicity of the ground flies, and the serum itself seemed 
even to contain some of the dissolved or liberated toxin. The 
slowness with which a lesion develops in the case of the black-fly 
bite supports the view of the initial lack of toxicity of the injected 
material. The entire absence of early subjective symptoms, such 
as pain, burning, etc., is further evidence for this view. It would 
appear as if no reaction occurred until lysis of an originally non¬ 
toxic substance had begun. Regarding the toxin itself as the chemo- 
tactic agent which attracts eosinophiles, its liberation in the lytic 
process and diffusion through the blood stream attracts the cells 
in question to the point at which it is being liberated. Arriving 
upon the scene, these cells assist in its neutralization. 

The last view presented is the one to which the author inclines 
as the one which most adequately explains the phenomena. 

A fourth view is that the initial injection of a foreign protein by 
the fly (i.e.,with the first bite) sensitizes the body to that protein. 
Its subsequent injection at any point in the skin gives rise to a 
local expression of systematic sensitization. Such local sensitization 
reactions have been described by Arthus and Breton, by Ham¬ 
burger and Pollack and by Cowie. The description of such a lesion 
given by the first named authors, in the rabbit, however, does not 
suggest, histopathologieally at least, a strong resemblance to that 
of the black-fly. Such an explanation of many insect urticaria 
deserves further investigation, however, and may align them under 
cutaneous expressions of anaphylaxis to a foreign protein injected 
by the insect. Depending on the chemical nature of the protein 
injected, a specific chcmotactic reaction like eosinophilia may or 
may not occur. Viewed in this light the development of immunity 
to insect bites assumes a place in the larger problem of anaphylaxis. 


Lesions Produced by the Bite of the Black-fly 


325 



174. Experimentaljesion produced from alcohol-fixed flies, dried and ground into a 
paste with glycerin. 








326 Lesions Produced by ike Bite of the Black-fly 


Summary 

In order to bring the results of the foregoing studies together, 
the author appends the following resume of the clinical data pre¬ 
sented in the first paper. 

The black-fly, Simulium venustum , inflicts a painless bite, with 
ecchymosis and haemorrhage at the site of puncture. A papulo¬ 
vesicular lesion upon an urticarial base slowly develops, the full 
course of the lesion occupying several days to several weeks. Marked 
differences in individual reaction occur, but the typical course in¬ 
volves four stages. These are, in chronological order, the papular 
stage, the vesicular or pseudovesicular, the mature vesico-papular or 
weeping papular stage and the stage of involution terminating in a 
scar. The papule develops in from 3 to 24 hours. The early pseudo¬ 
vesicle develops in 24 to 48 hours. The mature vesico-papular lesion 
develops by the third to fifth day and may last from a few days to 
three weeks. Involution is marked by cessation of oozing, subsidence 
of the papule and sear-like changes at the site of the lesion. The 
symptoms accompanying this cycle consist of severe localized or 
diffused pruritus, with some heat and burning in the earlier stages 
if the oedema is marked. The pruritus appears with the pseudo¬ 
vesicular stage and exhibits extraordinary persistence and a marked 
tendency to periodic spontaneous exacerbation. The flies tend to 
group their bites and confluence of the developing lesions in such 
cases may result in extensive oedema with the formation of oozing 
and crusted plaques. A special tendency on the part of the flies 
to attack the skin about the cheeks, eyes and the neck along the 
hair line and behind the ears, is noted. In these sites inflammation 
and oedema may be extreme. 

A distinctive satellite adeonpathy of the cervical glands develops 
in the majority of susceptible persons within 48 hours after being 
bitten in the typical sites. This adenopathy is marked, discrete 
and painful, the glands often exquisitely tender on pressure. It 
subsides without suppuration. 

Immunity may be developed to all except the earliest manifesta¬ 
tions, by repeated exposures. Such an immunity in natives of an 
infested locality is usually highly developed. There are also ap¬ 
parently seasonal variations in the virulence of the fly and variations 
in the reaction of the same individual to different bites. 

Constitutional effects were not observed but have been reported. 


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— - Spotted fever reports 1 and 2. In the 4th Bien. Rept. State Board of 

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Ricketts, H. T. and Wilder, R. M. 1910. The transmission of the typhus fever 
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Am. Med. Assoc, liv. p. 1304. 

Riley, C. V. and Howard, L. O. 1889. A contribution to the literature of fatal 
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Riley, W. A. 1906. A case of pseudoparasitism by dipterous larvae. Canadian 
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- 1910 a. Earlier references to the relation of flies to disease. Science 

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- 1910 b. Dipylidium caninum in an American child. Science n. s. xxxi, 

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- 1911. The relation of insects to disease. Cornell Countryman ix, 

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INDEX 


Abscess . 178 

Acanthia . 87 

Acariasis . 58 

Acarina . 23, 58, 131, 259 

Acarus dysenteriae . 132 

Accidental parasites . 131, 132, 134 

Aedes . 194, 293 

Aedes calopus. .. 182, 201, 205, 206, 208 

Aedes cantator . 101 

Aedes sollicitans . 101 

Aedes tceniorhynchus . 101 

Aerobic bacteria . 152 

Aestivo-autumnal . 186 

African Relapsing Fever . 230 

Akis spinosa . 177 

Alternation of Generations . 175 

Amblyomma . 264 

Amblyomma americanum . 67 

Amblyomma cajennense . 67 

American dog tick . 228 

Amoeboid organism . 189 

Anisolabis annulipes . 177 

Anterior poliomyelitis . 241 

Anopheles . 194, 291 

Anopheles crucians . 199 

Anopheles maculipennis . 182 

Anopheles punctipennis . 198 

Anopheles quadrimaculatus . 197 

Anopheline . 192 

Anthocoris . 279 

Anthomyiidae . 300 

Anthomyia . 138 

Anthrax . 165 

Antipruritic treatment . 72 

Ants . 42 

Aphiochaeta . 295 

Apis mellifica . 36 

Arachnida . 258 

Araneida . 6 

Argas . 64 

Argas persicus .. .63, 235, 237 

Argasidae . 62 

Argopsylla . 317 

Argus . 259 

341 


PACE 


Arilus. 


Arthopods, poisonous. . . . 

. 6 

Asopia farinalis. 

. 177 

Assassin-bugs. 

. 31. 219 

Auchmeromyia. 

. 1 17 

Automeris io. 

. 47 

Avicularoidea. 

. 12 

Babesia . 


Babesia bovis . 

. 223 

Babesia ovis. 

. 225 

Babesiosis . 


Bacilli. 

. 170 

Bacillus icteroides . 

....202, 205 

Bacillus pestis. 

. 166 

Bacillus typhosus. 

. 153 

Back swimmers . 

. 30 

Bdellolarynx. 

. 304 

Beauperthuy, Louis Daniel. 2 

Bed-bug.86, 88, 90, 

173,219-220 

Bed-bug, cone-nosed. 

. 92 

Blister beetles . 

. 54 

Belostoma. 

. 28, 277 

Belostoma americana . .. . 

. 3 i 

Belostomatidae . 

. 30 

Bengalia. 

. 314 

Bird-spiders . 

. 10 

Black death. 

.1, 166 

Black flies . 

.33, 104, 247 

Black heads. 


Blaps mortisaga. 

. 134 

Blepharoceridae. 

. 286 

Boophilus . 

. 264 

Boophilus annulatus. 

.67, 223-225 

Bot-flies. 

. 112 

Blue bottle flies. 

. 140 

Brill’s disease. 

. 238 

Brown-tailed moth. 

. 48 

Bruck. 

. 34 

Buthus quinquestriatus . . 

. 21 

Cabbage butterfly. 

. 56 

Calliphora . 

136,140, 312 

Calliphora erythrocephala 

. Hi 

























































































342 


Index 


Calobata . 


296 

Compsomyia . 

. 117 

Camponotinae. 


43 

Cone-nosed bed-bug .... 

. 92 

Cancer . 


254 

Conjunctivitis, nodular. 

. 52 

Cantharidin. 


54 

Conorhinus . 

. 282 

Cantharidin poison. 


55 

Conorhinus megistus. . . . 

.93,219-220 

Canthariasis . 


134 

Conorhinus rubrofasciatus . 220 

Capsidae. 


280 

Conorhinus sanguisugus. 

. 32, 92 

Carriers, simple. 

■ • - 4 . 

144 

Copra itch. 

. 72 

Carriers of disease . 


144 

Cordylobia . 

. 118 

Carrion’s fever. 


253 

Coriscus. 

. 280 

Caterpillar rash. 


45 

Coriscus subcoleoptratus 

. 32 

Cat flea . 


172 

Creeping myasis . 

. 112 

Cattle ticks. 


222 

Crustacea . 

. 257 

Causative organism. 


170 

Cryptocystis . 

. 176 

Cellia . 


291 

Cryptotoxic . 

. 54-55 

Centipedes. 

• 25, 

257 

Cteniza sauvagei . 

. 13 

Ceratophyllus. 

120, 

316 

Ctenocephalus . 120, 

172, 213,317 

Ceratophyllus acutus . 


123 

Culex . 

194,201, 293 

Ceratophyllus fasciatus ..122 

172, 

213 

Culex pipiens . 

. 35 , 98 

Ceratopogon. 


108 

Culex quinquefasciatus. . 

. 180 

Cheese-fly . 


137 

Culex sollicitans . 

. 200 

Cheyletus eruditus . 


271 

Culex territans . 

. IOI 

Chigger . 

. . .60, 70 

Culicidae . 

. 33 , 97 

Chigoes . 


126 

Culicin . 

. 34 

Chilopoda . 

• -25, 

257 

Culicoides . 

.... 109, 288 

Chiracanthium nutrix . 


18 

Cyclops . 

.... l8^. 2 S 7 

Chironomidae . 


107 

Cynomyia . 

— 136,311 

Chorioptes. 


270 



Chrysomelid. 


55 

Dance, St. Vitus . 

. 8 

Chrysomyia. 

136, 308 

Dancing mania . 

. 8 

Chrysomyia macellaria . 

•ii 7 . 

140 

Deer-flies . 

. IIO 

Chrysops . 


294 

Definitive host. 

. 192 

Chylous dropsy. 


179 

Demodecidae . 

. 78 

Chyluria . 


178 

Demodex . 

. 259 

Cicadidae . 


55 

Demodex folliculorum . . . 

. 78 

Cimex L . 


278 

Dermaeentor . 

. 262 

Cimex boueti . 


92 

Dermacentor andersoni . . 

00 

<N 

iC. 

Cimex columbarius . 


92 

Dermaeentor occidentalis. 

. 227 

Cimex hemipterus. 

91. 

220 

Dermacentor variabilis. . . 

. 67 

Cimex hirundinis . 


92 

Dermacentor venustus . . . 

. 24, 228 

Cimex inodorus . 


92 

Dermanyssidae . 

. 68 

Cimex lectularius . 

.. 87,219 

Dermanyssus . 

. 266 

Citheronia regalis . 


44 

Dermanyssus gallinas . . . . 

. 68 

Clinocoris . 


87 

Dermatitis . 

• - 72 , 77 , 85 

Coleoptera . 

134 . 

274 

Dermatobia . 

...IIS, 298 

Comedons . 


80 

Dcrmatobia cyaniventris . 

. 163 

Complete metamorphosis .... 


80 

Dermatophilus . 

. 317 

Compressor muscle . 


20 

Dermatophilus penetrans . 

. 60, 126 




































































































Index 


343 


Diamphidia simplex . 55 

Dimorphism . 65 

Direct inoculators . 4 

Diplopoda. . , . .. 25, 257 

Diptera . 33, 94, 274 

Dipterous Larvae . 135 

Dipylidium . 175,221 

Dipylidium canium . 4, 175-176 

Dog flea . 172 

Dracunculus . 257 

Dracunculus medinensis . 182 

Drosophila . 296 

Dum-dum fever . 220 

Dysentery . 154 

Ear-flies . no 

Earwig . 177 

Echidnophaga . 317 

Echinorynchus . 185 

Elephantiasis . 178-179 

Empoasca mali . 33 

Empretia . 46 

English Plague Commission . 171 

Epeira diadema . 18 

Epizootic . 170 

Eristalis . 137,295 

Essential hosts. 4, 165 

Eumusca . 307 

European Relapsing Fever . 233 

Euproctis chrysorrhoea . 48 

Eusimulium . 286 

Facultative parasites . 131 

Fannia . 136, 138, 145, 300 

Federal Health Service . 169 

Fever, lenticular . 237 

African Relapsing . 230, 234 

Carrion’s . 253 

dum-dum . 154 

European Relapsing. 233 

pappatici . 96 

red water . 220 

Rocky Mt. Spotted. 226 

three day . 96 

Typhus . 237 

Filaria . 178, 221 

immitis . 182 

Filariasis . 178 


Flannel-moth larvae. 

. 44 

Fleas . 

119, 166, 213 

cat . 

. 172 

dog . 

. 172 

human. 

.... 172, 176 

rodent . 

.... 123, 172 

rat . 

. 171 

Flesope. 

. 125 

Formaldehyde . 

. 91 

Fomites . 

. . . . 199, 204 

Fulgoridae . 

. 28 

Fumigation . 

. 320 

Gamasid . 

. 68 

Gangrene . 

. 129 

Gastrophilus. 

. 1 13,297 

Giant crab spiders. 

. 13 

Giant water bugs. 

. 30 

Gigantorhynchus. 

. 185 

Glossina. 

117, 297, 303 

Glossina morsitans. 

.... 214, 217 

palpalis. 

215, 217, 218 

Glyciphagus . 

. 267 

Grain moth . 

. 69 

Grocer’s itch. 

. 72 

Guinea-worm . 

. 182 

Habronema muscae . 

156, 183 

Haematobia . 

. 166, 304 

irritans. 

. 146 

Haematobosca . 

. 304 

Haematomyidium. 

. 288 

Haematopinus spinulosus 

. 213 

Haematopota . 

. 294 

Haematosiphon . 

. 279 

Haemoglobinuria . 

. 220 

Haemozoin . 

. 189 

Harpactor. 

. 284 

Harvest mites . 

. 60 

effect of. 

. 39 

Head-louse . 

. 173 

Helminthiasis. 

. 138 

Helophilus . 

. 295 

Hemiptera . 27 

, 86, 273-275 

Heteropodidae. 

. 13 

Heuchis sanguinea. 

. 55 

Hexapod larvae. 

. 58 

Hexapoda . 

...27, 80,258 































































































344 


Index 


Hippelates . 297 

Hippobosca . 285 

Histiogaster . 269 

spermaticus . 132 

Homalomyia . 136, 138,300 

Honey bee . 36 

poison of . 37 

Hornets . 43 

Horn-fly . 137, 304, 308 

Horse-fly . no, 165 

House-fly . I 37 -I 39 . 144 . 183 

control of . 156, 160 

Human flea .. 124 

Host, definitive . 175 

intermediate . 175 

primary . 175 

Hyalomma . 264 

aegypticum . 224-225 

Hydrocyanic Acid Gas . 318 

Hydrotaea . 300 

Hymenolepis diminuta . 176 

Hymenoptera . 36, 275 

Hypoderma . 113, 298 

diana . 113 

lineata . 113 

Hypopharynx . 80 


Jigger . 60 

Johannseniella . no, 288 

Journal of Tropical Medicine and 

Hygiene . 36 

Julusterrestris . 25 

June bug . 185 

Kala-azar . 220 

Kara, kurte . 14 

Katipo . 14 

King, A. F. A . 3 

Kircher, Athanasius . 1, 8 

Kissing-bug . 31 

Labium . 29, 80 

Labrum . 28, 80 

Lachnosterna . 185 

Laelaps . 266 

Lcemopsylla . 172 

Lagoa crispata . 45 

Lamblia intestinalis . 154 

Langer, Josef . 37 

Larder beetles . 135 

Latrodectus . 12, 14, 17 

mactans . 15 

Leishmanioses . 220 

Lenticular fever . 237 

Lepidoptera . 274 

Lepidopterous larvae . 134 

Leprosy . 252 

Leptidae . 112 

Leptis . 295 

Leptus . 60, 273 

Lice . 80 

Linguatulina . 258 

Liponyssus . 265 

Lone star tick . 228 

Louse, body . 84 

crab . 85 

dog . 176 

head . 82 

pubic . 85 

Lcemopsylla . 172, 317 

Lucilia . 136, 312 

Lycosa tarantula . 10 

Lycosidae . 10 

Lyctocoris . 279 

Lygus pratensis. 33 


Immunity from stings . 39 

Incomplete metamorphosis . 80 

Infantile paralysis.162,241 

splenic . 220 

Direct inoculation . 164 

Insects . 258 

blood-sucking . 170 

Intermediate host . 192, 203 

Intestinal infestation . 112, 133 

myasis . 137 

Isosoma . 69 

Itch . 73-74 

mite . 73 

Norwegian. 77 

Ixodes . 260 

ricinus. 66, 225 

scapularis. 66 

Ixodidae. 64-65 

Ixodoidea. 62 

Janthinosoma lutzi. 116 






























































































Index 


345 


Lymphangitis . 67 

Lymph scrotum . 178 

Lyperosia . 304 

Lyperosiops . 305 

Macloskie . 34 

Maggots, rat-tail . 137 

Magnes sive de Arte Magnetica. . 8 

Malaria . 186 

Malmigniatte . 14 

Mandibles . 28, 80 

Mange . 73-75 

Margaropus . 237, 264 

annulatus . 223 

Masked bed-bug hunter . 32 

Mastigoproetus giganteus . 19, 80 

Maxillae . 28 

Meal infesting species . 135 

Melanin granules . 189 

Melanolestes .. 280 

picipes . 32 

Mena-vodi . 14 

Mercurialis . 1 

Merozoites . 190 

Metamorphosis . 80 

Miana bug . 63 

Microgametoblast . 192 

Midges . 107 

Migratory ookinete . 192 

Millipedes . 25, 257 

Mites . 23, 58 

Monieziella . 269 

Mosquitoes . 33,97. 178, 196, 250 

treatment for bites of. . . .34, 36, 102 

Musca . 137,307 

domestica. . . . 139, 145, 146, 157, 162 

Muscidae . 117 

Muscina . 137, 146, 307 

stabulans . 140 

Mutualism . 57 

Myasis . 112, 135 

intestinal . 13 5-140 

nasal . 141 

Mycterotypus . 287 

Myiospila . 146,307 

Myriapoda . 25,132,257 

Nagana . 165,214 


Nasal infestation . 114, 133 

Necrobia . 135 

Nematode parasite . 182 

Nepa . 28 

Nephrophages sanguinarius . 132 

Nettling insects . 43 

larvae, poison of . 53 

N eurasthenia . 89 

Nits . 86 

North African Relapsing Fever. . 234 

Norwegian itch . 77 

No-see-ums . 109 

Notoedres . 269 

cati . 78 

Notonecta . 28, 277 

Notonectidae . 30 

Nott, Dr. Josiah . 2 

Nuttall . 34 

Occipital headaches . 138 

Oecacta . 288 

Oeciacus . 279 

CEsophageal diverticula. 35 

Oestridae . 112,136 

Oestris ovis . 113 

Oestrus . 298 

oocyst . 192 

ookinete . 192 

Opsicoetes personatus . 32 

Opthalmia . 155 

nodosa . 52 

Oriental sore . 221 

Omithodoros . 65, 260 

moubata . 220, 230 

Orthotvlus flavosparsus . 33 

Ornithomyia . 286 

Oroya . 253 

Oscinus . 297 

Otiobius . 259 

megnini . 65 

Otodectes . 271 

Pangonia . 294 

Pappatici fever. 96 

Parasimulium . 286 

Parasite . r. .3, 57, 131, 134, 182 

accidental . 3, 131, 134 

facultative. 3, 57, 131 



























































































346 


Index 


Parasite, nematode . 182 

stationary . 57 

temporary . 57 

true . 3 

Parasitism, accidental . 134 

Pathogenic bacteria . 152 

organisms . 144, 164 

Pawlowsky . 81 

Pediculoides . 267 

ventricosus . 69, 72 

Pediculosis . 81 

Pediculus . 275 

corporis . 84, 233, 238 

humanus . 82, 173 

Pellagra . 162, 246 

Pernicious fever . 186 

Pest . 166 

Phidippus audax . 19 

Philsematomyia . 306 

Phisalix . 13.43 

Phlebotomus . 289 

papatasii . 94 

verrucarum . 254 

vexator . 95 

Phora . 295 

Phormia . 136 

Phormictopus carcerides . 13 

Phthirus pubis . 85, 275 

Phortica . 296 

Pieris brassicae . I.'V ! 56 

Piophila . 297 

Piophila casei . 136, 137 

Piroplasmosis . 222 

Plague . 166 

bubonic . 166, 169, 170 

pneumonic . 167 

Plasmodium . 186 

Platymetopius acutus . 33 

Plica palonica . 83 

Pneumonic . 166 

plague . 167, 173 

Poisoning by nettling larvas. 53 

Poison of spiders . 7 

Pollenia . 308 

rudis . 146, 147 

primary gland . 28 

Prionurus citrinus . 20 

Prosimulium . 286 


Protocalliphora . 136, 312 

Protozoan blood parasite . 165 

Pseudo-tubercular . 52 

Psorophora . 293 

Psoroptes . 270 

Psychodidag . 94 

Pulex . 120, 124, 126, 172,317 

cheopis . 172 

irritans . 124 

penetrans . 126 

serraticeps . 120 

Pulvillus . 150 

Punkies . 109 

Pycnosoma . 308 

Rasahus . 280 

thoracicus . 32 

Rat fleas . 120, 124,171 

Rat louse . 213 

Red bugs . 70-72 

Reduviidae . 31 

Reduviolus . 280 

Reduvius . 282 

personatus . 32 

Red water fever . 220 

Relapsing fever . 230, 233 

Rhinoestrus nasalis . 115 

Rhipicentor . 264 

Rhipicephalus . 264 

Rhizoglyphus . 269 

Rhodnius . 280 

Rocky Mountain Spotted Fever. . 226 

spotted fever tick . 67 

Russian gad-fly . 115 

St. Vitus’s or St. John’s dance. ... 8 

Salivary syringe . 28 

Sand-flies . 109, 250 

Sanguinetti . 11 

Sarcophaga . 136, 142, 143 

Sarcophila . 302 

Sarcopsylla . 317 

penetrans . 126 

Sarcoptes . 270 

minor . 78 

scabiei . 73 

Sarcoptidae . 72 

Scabies. 72, 73, 74, 75 































































































Index 


Scaurus striatus . 177 

Schaudinn . 34 

Schizont . 189, 190 

Scholeciasis . 134 

Scolopendra morsitans .. 26 

Scorpions . 20 

poison of . 21 

Screw worm fly . 140 

Sepsidse . 296 

Sepsis . 136, 297 

Shipley . 34 

Sibine . 46 

Silvius . 294 

Simple carriers . 4, 144 

Simuliidae . 33, 104 

Simulium . 247, 249, 286, 321 

pictipes . 104 

Siphonaptera . 119, 274, 316 

Siphunculata . 80, 275 

Sitotroga cerealella . 69 

Skippers . 137 

Sleeping sickness . 166, 215 

Snipe-flies . 112 

Solpugida . 22 

Spanish fly . 54 

Spermatozoa . 192 

Spinose ear-tick . 65 

Spirochoeta . 35 

berberi . 234 

duttoni . 234 

Spirochaetosis . 235 

Sporozoite . 189 

Spotted fever . 67, 226 

Squirrel flea . 123 

Stable-fly . 137, 160, 163, 165 

Stegomyia . 182, 293 

calopus . 206 

fasciata . 206 

Stomoxys . 137, 305 

calcitrans 117, 146, 160, 161, 165, 242 

Straw-worm . 69 

Stygeromyia. 305 

Sucking stomach. 35 

Sulphur ointment. 77 

Surra . 165 

Symbiosis . 57 

Symphoromyia. 112, 295 


347 


Tabanidae . no 

Tabanus . no, 166, 294 

striatus . 165 

Taenia . 175 

Tapeworm . 4, 176 

Tarantella . 8 

Tarantism . 8 

Tarantula . 10 

Tarsonemidae . 69 

Tarsonemus . 267 

Tenebrionid beetles . 127 

Tersesthes . no, 288 

Tetanus . 129 

Tetranychus . 273 

Texas fever . 220-223 

Three-day fever . 96 

Tick . 23, 226 

bites, Treatment of . 68 

fever . 230 

paralysis . 67 

Treatment, 

Bee stings . 36, 41 

Bites of, 

Bed-bugs . 90,93 

Blackflies . 107 

Buffalo flies . 107 

Bugs . 31, 33 

Centipedes . 26, 27 

Chiggers . 127 

Chigoes . 127 

Fleas . 127 

Harvest mites . 61 

Jiggers . 129 

Lice . 83,85 

Mosquitoes . 34, 36, 102 

Phlebotomus flies . 97 

Sand flies . 96, 107, 109 

Scorpions . 22,23 

Spiders . 19 

Ticks . 61,68,72 

Ticks, ear . 65 

Blister beetle poison . 55 

Brown-tail moth rash . 45 

Cantharidin poison . 55 

Caterpillar rash . 45 

Ear ticks . 65 

House fly control . 156, 160 

Itch . 77 































































































348 


Index 


Itch, grocer’s . 72 

Lice . 85 

Nasal myasis . 143 

Rocky Mt. spotted fever. . .228, 229 

Rash, caterpillar . 45 

Scabies . 77 

Sleeping sickness control . 218 

Spotted fever . 228, 229 

Stings, bee . 36, 41 

Typhus fever, prophylaxis . 239 

Trichodectes canis . 176 

Trichoma . 82 

Trineura .. 295 

Trochosa singoriensis . 11 

Trombidium . 60, 273 

True insects . 80 

T ry panosoma . 35 

Trypanosoma, brucei . 165 

Trypanosoma cruzi . 219 

Trypanosoma lewisi . 213 

Trypanosomiases . 212 

Trypanosomiasis . 165,219 

Testse flies . 117, 166, 214, 219 

Tsetse flies disease . 165 

T uberculosis . 155 

Tumbu-fly . 118 

Tydeus . 271 

Typhoid . 155 


Typhoid fever . 154 

Typhus . 237 

Typhus fever . 237 

Tyroglyphus . 72, 131, 268 

Dr. Tyzzer . 49 

Uranotaenia . 292 

Vancoho . 14 

Varicose groin glands . 178 

Verruga peruviana . 253 

Vescicating insects . 54 

Wanzenspritze . 29 

Warble-flies . 112 

Wasps .. 43 

Whip-scorpions . 19 

Wohlfahrtia . 143, 302 

Wolf-spiders . 10 

Wyeomyia smithii . 101, 293 

Xenopsylla . 172, 317 

Xenopsylla cheopis . 171, 124 

Xestopsylla . 317 

Yaws . 2 

Yellow fever . 196, 203, 205